Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

We report on the pulsed-laser-deposition (PLD) based nanodecoration of LiCoO₂ (LCO) with BaTiO₃ (BTO) nanoparticles (NPs) aimed at increasing the density of dielectric-active material–electrolyte triple-phase interfaces (TPIs). The BTO-NPs were deposited onto LCO at different numbers of laser pulses (N_Lp) and two different schemes, namely, (i) BTO-NP deposition on the surface of the precast cathode (“2D-nanodecoration”) and (ii) BTO-NP decoration of LCO powder prior to its processing to form a working cathode (“3D-nanodecoration”). While the “2D-nanodecoration” mode was found to improve significantly the discharge capacity of the LCO cathodes (by ∼30 mAh/g for N_Lp ≥ 200), their capacity retention (CR) was modest. In contrast, the “3D-nanodecoration” scheme enabled not only the volumic nanodecoration of the LCO powder by BTO-NPs but also their subsequent annealing to improve their crystallinity. These 3D-nanodecorated LCO cathodes were found to exhibit significantly higher CR values. In particular, for N_Lp = 100 k, a CR (@10 °C) as high as 78% was achieved (∼47% higher than that of their sol–gel-processed cathode counterparts). Our results point out that three key ingredients (small BTO-NP size, high D_TPI, and high dispersibility of NPs on LCO) should be combined to ensure a high CR of BTO-NP-decorated LCO cathodes.

DOI： 10.1063/5.0075970

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

The applicability of rice husks to solid phase foaming ceramics was assessed. Through an atmospheric heat treatment on silicon carbide based mixture produced by the reduction heat treatment of rice husks, the residual carbon was mostly eliminated, giving a foaming agent composed of approximately SiC and SiO2. Solid-phase foamed porous ceramics was fabricated using this rice husk-derived foaming agent and the properties were compared with that fabricated from commercially available SiC. The sample fabricated from the rice husk-derived foaming agent showed favorable performances in terms of both strength and heat insulating properties. In comparison with the sample fabricated by adding commercially available silica in addition to commercial SiC, the strength became comparable, however, its heat insulating property was still inferior to that using rice husk-derived foaming agent. The increase in mechanical strength can be ascribed to the suppression of the grain growth due to the added silica. The formed silica phase existing at the grain boundaries would affect the thermal conductivity.

DOI： 10.1007/s10934-021-01156-3

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Other Link： https://link.springer.com/article/10.1007/s10934-021-01156-3/fulltext.html

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Drastic enhancement in the high-rate capability of lithium-ion batteries to the level of supercapacitors while maintaining high energy density is required for next-generation power sources. Incorporating dielectric BaTiO3 (BTO)-based nanocubes (NCs) into the active materials-electrolyte interface provides an ultrafast charge transfer pathway via the dielectric layer. The highly dispersed NC-decorated LiCoO2 (LCO) treated at the optimized temperature of 600 degrees C displays significantly enhanced high-rate capability; the cell maintains 56.7 mAh g(-1) at 50C (1C = 160 mA g(-1)), which compares with null capacity at the same rate for bare LCO. Comparing the NCs with conventional sol-gel-derived nanoparticles, the capacity retention at 10C (vs 0.1C) steadily increases with increasing active materials-dielectric-electrolyte triple-phase interface (TPI) in the NC-decorated case, whereas the capacity retention decreases markedly at similar TPI density in the sol-gel case. In the sol-gel case, the amount of Li ions accumulating at the TPI greatly exceeds the maximum amount of Li ions involved in electron exchange through the redox reaction within the charge/discharge time. In the NC case, most Li ions at the TPI participate effectively in the redox reaction, which results in fast charge transfer since the TPI sites are abundantly supplied with Li ions.

DOI： 10.1002/admi.202101682

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

We deposited polar-axis-oriented tetragonal and rhombohedral single domain Pb(Zr, Ti)O-3 (PZT) films on CaF2(100) substrates by inserting SrRuO3 (SRO)/LaNiO3 and SRO/SrTiO3/TiO2/CeO2 buffer layers. Both PZT films grew epitaxially and had a (001)- and (111)-domain with the remnant polarization and piezoelectric constant comparable to the theoretical values of PZT single crystals having the same compositions. The electro-optic (EO) response of the fabricated PZT films was constant with respect to the DC electric field and increased linearly with an increasing AC electric field, thus representing a typical linear EO response in single domain ferroelectrics. The measured EO coefficients were larger than the value for a single crystal of PbTiO3, i.e., one of the end members of PZT, but smaller than the values reported for polycrystalline and epitaxial PZT films with multiple domains. These findings show that the intrinsic EO effect is enhanced in PZT, which is similar to the enhancement seen in the dielectric and piezoelectric constants. Moreover, most of the reported EO response in PZT films is supported by additional extrinsic contributions.

DOI： 10.1063/5.0056121

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.35848/1347-4065/ac17e0

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

<title>Abstract</title>
Electro-optic (EO) modulators for silicon photonics using CMOS-compatible materials and processes are in great demand. In this study, epitaxial (100)-undoped HfO₂ and Y-doped HfO₂ thin films were fabricated on Sn-doped In₂O₃/yttria-stabilized zirconia(100) substrates at room temperature via magnetron sputtering. EO measurement of the Y-HfO₂ film using modulation ellipsometry showed that the phase was changed by 180° after application of positive and negative poling biases, and the modulation amplitude increased linearly with increasing AC electric field, indicating a linear EO effect based on ferroelectricity. The observed results indicate that ferroelectric HfO₂-based films are viable candidates for CMOS-compatible EO devices.

DOI： 10.35848/1347-4065/ac087d

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jpowsour.2021.229710

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A novel colossal polarization architecture generated at the fast Li-ion conductor-dielectric interface is proposed. A fast Li-ion conductor, La0.57Li0.29TiO3 (LLT), is utilized as the conductive core material, while the ferroelectric barium titanate (BaTiO3; BT) was coated onto the LLT as the shell layer via a liquid phase reaction. After densification of the composites, the shell BT fully transforms into the interdiffusion layer, i.e. (Ba, Li, La)TiO3 (BLLT). The BLLT effectively hinders Li diffusion, leading to a colossal polarization at the core-shell interface. Consequently, the optimized BT-LLT achieves dielectric characteristics at 1 kHz with permittivity of 3.28 x 10(4).

DOI： 10.35848/1347-4065/abf088

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

A ceria-based solid electrolyte was temporarily strengthened via the chemical expansion that occurred during contact reduction of its surface. One side of a non-doped ceria ceramic or 8 mol% samaria-substituted ceria ceramics was placed on a carbon sheet and heat-treated at various oxygen partial pressures and temperatures. Heat treatment increased the mechanical strength by up to 30%. The annealing temperature at which the samaria-substituted ceria had the highest strength was lower than that for the non-doped ceria. Both ceria ceramics had almost the same electrical conductivity regardless of whether they were untreated, subjected to contact reduction, or oxidatively heat-treated. (C) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2020.127712

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.67.163

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.7567/1347-4065/ab39f4

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Authorship：Lead author,　Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.66.73

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.65.475

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

Here, as with previous work, atomic layer deposition (ALD) has been used to deposit Al2O3 on positive electrode active materials, LiCoO2, to create a protective barrier layer, suppress the high potential phase transition, and thus reduce the subsequent Co dissolution. However, in this study it was found that it also resulted in the reduction of the charge transfer resistance at the positive electrode-electrolyte interface, thus enhancing the performance of the battery. Energy-dispersive X-ray spectroscopy, in conjunction with transmission electron microscopy, shows that a discrete Al2O3 shell was not formed under the selected growth conditions and that the Al diffused into the bulk LiCoO2. The resulting active oxide material, which was significantly thicker than the nominally ALD growth rate would predict, is proposed to be of the form LiCoO2:Al with amorphous and crystalline regions depending on the AI content. The cells consisting of the modified electrodes were found to have good cycling stability and discharge capacities of similar to 110 mA h g(-1) (0.12 mA h cm(-2)) and similar to 35 mA h g(-1) (0.04 mA h cm(-2)) at 50 and 100 C, respectively.

DOI： 10.1021/acsaem.8b00496

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

On-board vehicle applications dictate the need for improved low-temperature power densities of rechargeable batteries. Integration of high-permittivity artificial dielectric solid electrolyte interfaces (SEIs) into the lithium ion battery architecture is a promising path to satisfy this need. The relationship between the permittivity of various artificial dielectric SEIs and the resulting high-rate capability at low temperatures is investigated. Room-temperature studies reveal a weak relationship between these variables. However, at low temperatures, the correlation between the larger permittivity of the dielectric SEIs and the greater high-rate capabilities of the cells is striking. The high-rate capabilities for pulsed laser deposition-synthesized cathode thin films with various BaTiO3 (BTO) SEIs covering configurations are evaluated. A remarkable improvement in the high-rate capability is observed for LiCoO2 (LCO) modified with dot BTOs, while the rate capability for planar BTO (fully covered LCO) is weakened significantly. A series of experimental results prove that a large polarization, P, in the dielectric SEIs intensified with permittivity accelerates interfacial charge transfer near the dielectrics-LCO-electrolyte triple junction.

DOI： 10.1002/aelm.201700413

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Domain engineering via oxygen vacancy, VO loading achieved by A/B modification as well as quenching treatment, was utilized for Ba0.8Sr0.2TiO3 (0.8 BSTs) in an attempt to enhance the microwave tunable characteristics. For similar grain sizes, the domain sizes were notably reduced for all nonstoichiometric BSTs, indicating that the loaded VO.. (as a consequence of Ti defects, VTi) played a role in the nuclei for new domain walls. The tunability T at 100 MHz under a direct current field of 30 V/20 m increased steadily as the domain size (d.s.) declined for all BSTs, regardless of the A/B ratio, due to the d.s. effect. The tunable characteristics in nonstoichiometric BSTs having a similar d.s. of 190 nm were then compared. The tunability and tan decreased for A/B = 1.002 (0.2 mol% Ti defects). The introduced VO.. formed pinning centers that restricted domain wall motion, leading directly to lower tunability and smaller dielectric loss. However, VO..-overloaded samples (i.e., A/B 1.005) exhibited increased values for tan due to VO.. conduction in the domains. The quench treatment of 0.8 BST (with A/B = 1.002) samples resulted in a d.s. reduction from 191 to 170 nm. These quenched specimens showed greater tunability, T-total, originating from the strengthened dipole contribution, T-dipole, as a consequence of the d.s. effect. The tan of the quenched specimens was essentially unchanged, indicating a homogenous VO.. distribution via the quench, effectively reducing the mobile VO.. (which contributes to electrical conduction) in the domains. Consequently, the achieved figure of merit via domain engineering was 2.25 at 100 MHz for the quenched BST with A/B = 1.002, which was 1.54 times larger than that of unmodified BST.

DOI： 10.1111/jace.15242

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We decorated nano-crystalline LiNbO3 (LN) particles, which played the role of artificial solid electrolyte interfaces (SEIs) on an active material, namely LiCoO2 (LC). Conventional one-step synthesis using metal organic decomposition (MOD) was used initially, but resulted in the presence of an undesired Li-rich compound, Li3NbO4 (L3N), along with a counterpart phase, Co3O4. Hence, we incorporated crystalline LN into the LC matrix via a two-step synthesis method. Treatment at 500-700 degrees C resulted in single-phase LN-decorated LCs with improved high rate capabilities. The improvement in the rate capability is related to the temperature dependencies of the two most important parameters: 1) the degree of LN crystallinity, which corresponds to the improvement in the polarization, and 2) the density of the triple phase junctions, which act as active Li ion pathways. The optimized capacity, 78 mAh/g at 20 C, of the specimen annealed at 600 C was 20 C, which is approximately 1.7-fold larger than that of amorphous LN-decorated LC and is 2.6 times higher than that of bare LC. This implied the introduction of a dielectric polarization architecture had a greater impact on the improvement to the rate capability than Li transportation through the amorphous LN.

DOI： 10.1016/j.ssi.2017.11.020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

High operation temperature of solid oxide fuel cell (SOFC) results in high cell and operation cost, time consuming and fast cell degradation. Developing high performance SOFC that operates at lower temperature is required. Here we demonstrate 24 GHz microwave as a rapid heating source to replace conventional heating method for SOFC operation using 20 mol% Sm doped CeO2 electrolyte-supported single cell. The tested cell shows improvement of 62% in maximum power density at 630 °C under microwave heating. This improvement governs by bulk conductivity of the electrolyte. Investigation of ionic transference number reveals that the value is unchanged under microwave irradiation, confirming the charge carrier is dominated by oxygen ion species. This work shows a potential new concept of high performance as well as cost and energy effective SOFC.

DOI： 10.1016/j.jpowsour.2017.11.036

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.65.21

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Cyclic characteristics of BaTiO3 (BT)-decorated LiCoO2 (LC), for use as an artificial solid electrolyte interface (SEI) were evaluated at high voltages. Within the standard voltage window (i.e., 3.3-4.2 V), the BT-decorated LC exhibited greater capacities for up to 80 cycles compared with both the Al2O3 (paraelectric)-decorated and bare LC SEIs. The discharge capacity retention after 80 cycles (compared with the initial value) was 86.0% for the BT-LC cathode. This is a significant improvement over both the bare LC that showed 19.9% retention and the Al2O3-LC that displayed 71.5% retention. Thereafter, the cyclic stabilities of the BT-LC and bare LC were compared within potential windows at cutoff voltages as high as 4.9 V. In this region, BT decoration yielded marked improvements in capacity retention after 50 cycles, up to a potential of 4.7V. The post-situ XRD analysis of the cathode sheets showed that BT decoration effectively stabilized the hexagonal crystal structure of the LC, H1, resulting in the said cyclic stability increase. These observations demonstrate that the use of BT in SEI allows a significant increase in working voltage while maintaining the chemical stability of the underlying LC matrix, a key advancement in the perpetual pursuit of ever higher cell energy densities. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.10PC01

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Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.68.401

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Films of the relaxor ferroelectric BaZr0.25Ti0.75O3 (0.25-BZT) were synthesized via a sol-gel route to investigate the effect of film thickness on the dielectric properties and for comparison with normal ferroelectric BaTiO3 (BT). The as-prepared films on Nb-doped SrTiO3 (Nb-ST) displayed a (100) orientation; thinner films had stronger (100) orientations. Microwave dielectric measurements up to a few GHz quantified the polarizations, that is, the dipole contribution, epsilon(dipole), the combination of the ionic and electronic polarizations, epsilon(ionic+el.), and the total contribution, epsilon(total). The epsilon(dipole) in the relaxors at a film thickness of t=630nm was 360, which was double that for the normal ferroelectric BT (epsilon(dipole)=180) at t=735nm. The larger apparent permittivity of the BZT therefore originated from the larger epsilon(dipole) of the polar nanoregions (PNRs), while the nanograins of BT with few domain walls led to a comparably smaller epsilon(dipole). The volume ratio of the surface and film-substrate interface lacking the dipole interactions increased with the reduction in the film thickness, leading to the significant depression in the permittivity for both specimens. The difference in the thickness dependence of the dielectric properties of the sol-gel derived relaxor BZT and the normal ferroelectric BT films was attributed to the different origins of their dipole contribution, that is, the PNRs and ferroelectric domains, respectively.

DOI： 10.1111/jace.14768

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

The impact of the (Ba + Sr)/Ti (A/B) ratio on the microwave-tunable characteristics of diffuse phase transition (DPT) ferroelectric Ba0.6Sr0.4TiO3 (0.6-BST) ceramics was investigated. The reduction in the lattice constant with increasing nonstoichiometry was attributed to introduced partial Schottky defects, i.e., [V ''''(Ti) - 2V(O)(center dot center dot)](x) and [V ''(Ba,Sr) - V-O(center dot center dot)](x). The magnitude of the dielectric constant, epsilon', at room temperature in the absence of an applied electric field was governed by the shift in the dielectric maximum temperature, T-m, because T-m was close to room temperature for the 0.6-BST. The dielectric loss, tan delta, diminished as the epsilon' decreased for 0.98 &lt;= A/B &lt;= 1.05, while the tand was much higher for A/B=0.95 having the greatest A-site vacancy loading. The negatively charged V ''(Ba) and V ''(Sr) were mainly compensated by oxygen vacancies and likely partly compensated by holes, h(center dot), which contributed to the electrical conduction. The tunability, T, at 100 MHz was almost constant at 20%-25% for A/B &gt;= 1.00 despite the reduction of the epsilon', whereas T decreased for A/B&lt;1.00 to ca. 10% for A/B=0.95 having the greatest A- site vacancy loading. The results implied that the [V ''''(Ti) - 2V(O)(center dot center dot)](x) for larger A/B values was more efficient in generating nucleation sites in the polar nanoregions (PNRs) than the [V ''(Ba,Sr) - V-O(center dot center dot)](x) for smaller A/B values, thereby providing greater dipole polarization. Consequently, the figure of merit, FOM, reached its maximum of 250 at A/B=0.9875, which was ca. 155% higher than that of the stoichiometric BST.

DOI： 10.1111/jace.14700

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The electrical conductivity of promising candidates for intermediate temperature solid oxide fuel cell (IT-SOFC) electrolyte; 10-25 mol% gadolinium or samarium-doped CeO2 was measured through impedance measurement under millimeter-wave irradiation heating. Conductivity value for all samples was found to be higher when measured under millimeter-wave irradiation heating than that measured under conventional heating. Results from activation energy show that energy for cation-vacancy dissociation was largely affected bymillimeter-wave irradiation, where significant reduction was observed, thus improved the conduction process. Possibility of contribution from non-thermal ponderomotive force in conduction process was discussed. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.matdes.2016.11.051

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Authorship：Corresponding author   Language：Japanese  

CiNii Article

CiNii Books

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Improving the conductivity of 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte has enabled a lowering of the operating temperature of solid oxide fuel cells. We previously reported that millimeter-wave irradiation heating increases the ionic conductivity of ceramics. The ionic conductivity of 8YSZ under millimeter-wave irradiation heating had been up to 20 times higher than that with conventional heating. In the present study, we investigated the optimal thermal environment for millimeter-wave irradiation heating. We also investigated the thermal profile of samples under millimeter-wave irradiation heating to elucidate the rate of the non-thermal effect. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.17056

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Metal organic decomposition (MOD) using octylic acid salts was applied to synthesize a BaTiO3-LiCoO2 (BT-LC) composite powder. The Ba and Ti octylates were utilized as metal precursors, in an attempt to synthesize homogeneous BT nanoparticles on the LC matrix. The BT-LC composite, having a phase-separated composite structure without any impurity phase, was successfully obtained by optimizing the MOD procedure. The composite prepared using octylate precursors exhibited a sharper distribution and better dispersibility of decorated BT particles. Additionally, the average particle size of the decorated BTs using metal octylate was reduced to 23.3 nm, compared to 44.4nm from conventional processes using Ba acetate as well as Ti alkoxide as precursors. The composite cathode displayed better cell performance than its conventional counterpart; the discharge capacity of the metal octylate-derived specimen was 55.6mAh/g at a 50C rate, corresponding to 173% of the capacity of the conventional specimen (32.2mAh/g). The notable improvement in high rate capability obtained in this study, compared with the conventional route, was attributed to the higher density of the triple junction formed by the BT-LC-electrolyte interface. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.10TB01

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

The preparation of a stable suspension dispersing carbon nanotube (CNT) in aqueous media using polystyrene maleic acid (PSMA)-based polymer as surfactant was attempted to be subsequently used in the fabrication of high-performance ceramic matrix composites. Settling velocity under centrifugation analysis was experimentally evaluated as one of the stability criteria of the dispersion and pulsed nuclear magnetic resonance was used to evaluate the amount of adsorbed molecules. The settling velocity decreased considerably with the PSMA concentration up to the saturation at around 7 mass%, then further decreased gradually with PSMA. The former was thought to be based on the dissociation of CNT agglomerate and the latter would be attributed to the surfactant-induced network structure formed in the aqueous media.

DOI： 10.2497/jjspm.63.861

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Language：English   Publisher：Institute of Physics  

Metal organic decomposition (MOD) using octylic acid salts was applied to synthesize a BaTiO<inf>3</inf>–LiCoO<inf>2</inf>(BT–LC) composite powder. The Ba and Ti octylates were utilized as metal precursors, in an attempt to synthesize homogeneous BT nanoparticles on the LC matrix. The BT–LC composite, having a phase-separated composite structure without any impurity phase, was successfully obtained by optimizing the MOD procedure. The composite prepared using octylate precursors exhibited a sharper distribution and better dispersibility of decorated BT particles. Additionally, the average particle size of the decorated BTs using metal octylate was reduced to 23.3 nm, compared to 44.4 nm from conventional processes using Ba acetate as well as Ti alkoxide as precursors. The composite cathode displayed better cell performance than its conventional counterpart; the discharge capacity of the metal octylate-derived specimen was 55.6 mAh/g at a 50C rate, corresponding to 173% of the capacity of the conventional specimen (32.2 mAh/g). The notable improvement in high rate capability obtained in this study, compared with the conventional route, was attributed to the higher density of the triple junction formed by the BT–LC–electrolyte interface.

DOI： 10.7567/JJAP.55.10TB01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Torsional forced-oscillation experiments on a suite of synthetic MgO polycrystals, of high-purity and average grain sizes of 1-100 mu m, reveal strongly viscoelastic behavior at temperatures of 800-1300 degrees C and periods between 1 and 1000s. The measured shear modulus and associated strain energy dissipation both display monotonic variations with oscillation period, temperature, and grain size. The data for the specimens of intermediate grain size have been fitted to a generalized Burgers creep function model that is also broadly consistent with the results for the most coarse-grained specimen. The mild grain size sensitivity for the relaxation time (L), defining the lower end of the anelastic absorption band, is consistent with the onset of elastically accommodated grain boundary sliding. The upper end of the anelastic absorption band, evident in the highest-temperature data for one specimen only, is associated with the Maxwell relaxation time (M) marking the transition toward viscous behavior, conventionally ascribed a stronger grain size sensitivity. Similarly pronounced viscoelastic behavior was observed in complementary torsional microcreep tests, which confirm that the nonelastic strains are mainly recoverable, i.e., anelastic. With an estimated activation volume for the viscoelastic relaxation, the experimentally constrained Burgers model has been extrapolated to the conditions of pressure and temperature prevailing in the Earth's uppermost lower mantle. For a plausible grain size of 10mm, the predicted dissipation Q(-1) ranges from similar to 10(-3) to similar to 10(-2) for periods of 3-3000s. Broad consistency with seismological observations suggests that the lower mantle ferropericlase phase might account for much of its observed attenuation.

DOI： 10.1002/2016JB013126

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Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

Our innovative superplastically foaming method was used to create closed-pore inclusive zirconia-based ceramics. Yttrium oxide was added to monoclinic zirconia to stabilize the matrix. Sintering and superplastic deformation were used to form a solid solution and transform it to a cubic phase. Porous ceramics formed via this post-stabilization method exhibited anomalous thermal expansion due to the silica derived from the foaming agent SiC. This anomalous thermal expansion disappeared following substitution of the SiC foaming agent for AlN. The resulting superplastically foamed porous ceramics exhibited large thermal conductivities, comparable to that of the fully densified ceramics, but with a porosity as great as 35%. This high thermal conductivity was attributed to the alumina derived from the foaming agent AlN. To suppress the formation of alumina, the samples were pre-sintered in an argon atmosphere. The modified superplastically foamed ceramics exhibited smaller pores, with a porosity of 33%, as well as favorable thermal insulation, with a thermal conductivity that was approximately half that of the fully dense material.

DOI： 10.1002/9781119234463.ch7

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Lithium lanthanum titanates (Li3xLa2/3 - xTiO3, LLTOs) having a-axis orientations were synthesized via a simple sol-gel route on SrTiO3 and Nb-doped SrTiO3 substrates. The lithium ion conduction behaviors of the LLTO films were determined. Annealing the films above 1200 degrees C yielded strong a-axis growth orientation, while heating samples above 1300 degrees C led to the reduction of the Li transference number, T-Li, which was attributed to Li evaporation. The optimized annealing temperature was 1200 degrees C, where both the bulk conductivity, sigma(dc) and the T-Li exhibited their maxima. The bulk conductivity was 4.42 x 10(-5) S/cm for a 411-nm-thick film, which was almost 10-times-higher than that previously reported for sol-gel-derived films. A key reason for the enhancement in conductivity is the expanded bottleneck of the LLTO lattice because of a tensile stress induced by the substrate. Optimization of the annealing temperature and the film thickness further improved the conductivity. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2015.11.029

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Authorship：Last author,　Corresponding author   Language：English   Publisher：Japan Society of Powder and Powder Metallurgy  

<p>Sm-doped CeO₂ ceramics were prepared by conventional solid state method. The electrical conductivity of the samples was measured under conventional heating and 24 GHz millimeter-wave (MMW) heating, and the results were compared. During MMW heating, 5 mol% Sm-doped CeO₂ pellets with different thickness were used as susceptors, meanwhile Al₂O₃ fiber board was used as thermal insulator and its design varies by the number of open channels. The aforementioned susceptors and thermal insulators dependency of conductivity values during MMW heating were studied. Conductivity of samples under MMW heating was found to be higher than under conventional heating. Results showed that the different susceptor thickness and thermal insulator design could result in different conductivity values. These results were attributed to the phenomenon of heat dissipation from surface and the amount of direct radiation reached the sample. Specific susceptor thickness and specific insulator design which leads to highest conductivity were identified. By combining these two effects, the largest enhancement of conductivity of ceria based ceramics was obtained.</p>

DOI： 10.2497/jjspm.63.663

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

In this study, in situ time-resolved dispersive X-ray absorption fine structure (DXAFS) analysis of BaTiO3-LiCoO2 (BT-LC) composites for lithium ion batteries was performed to characterize the cobalt ion valence shift between oxidized and reduced states of driven cells, in an attempt to better understand the contribution of ferroelectric solid electrolyte interfaces (SEIs) to charge-discharge rates. Two types of artificial SEIs, ferroelectric BT and paraelectric Al2O3, were compared. The magnitude of the shift in the X-ray absorption energy at the peak of the white line, E-1, during charging and discharging at a 10C rate, increased in the order of bare LC (0.264 eV) &lt; Al2O3 1 mol% (0.497 eV) &lt; BT 1 mol% (1.15 eV); the corresponding discharge capacities of the laminated cells at 10C were as follows: bare LC (11.6mAh/g) &lt; Al2O3 (41.8mAh/g) &lt; BT (95.1mAh/g). The increase in E1, i.e., the oxidation of Co during charging, intensified under a higher applied potential for the BT-decorated composite compared with that of the Al2O3-coated specimen. The stronger oxidation of Co for BT-LC under application of a large electric field was attributed to the strengthened polarization due to the larger permittivity of BT. (C) 2016 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.16009

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.63.981

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

The preparation of a stable suspension dispersing carbon nanotube (CNT) in aqueous media using polystyrene maleic acid (PSMA)-based polymer as surfactant was attempted to be subsequently used in the fabrication of high-performance ceramic matrix composites. Settling velocity under centrifugation analysis was experimentally evaluated as one of the stability criteria of the dispersion and pulsed nuclear magnetic resonance was used to evaluate the adsorbed molecules. The settling velocity decreased considerably with the PSMA concentration up to the saturation at around 7 mass%, then further decreased gradually with PSMA. The former was thought to be based on the dissociation of CNT agglomerate and the latter would be attributed to the surfactant-induced network structure fanned in the aqueous media.

DOI： 10.2320/matertrans.Y-M2015828

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Ionic conductivity was measured on scandia-, calcia-, and gadolinia-stabilised zirconia ceramics under quasi-millimeter-wave (MMW) irradiation heating and conventional heating. Conductivity enhancement was evaluated for these ceramics and compared with our previous report on yttria- and ytterbia-stabilised zirconia ceramics (YSZ and YbSZ, respectively). The ionic conduction for the various cation-substituted zirconia ceramics was enhanced under MMW irradiation heating. In the case of scandia-stabilisation, the optimal composition demonstrating maximum ionic conductivity was 12-mol% zirconia (ScSZ) under MMW irradiation heating, which was larger than under conventional heating. Such an optimal composition shift was similar to results for YSZ ceramics. These results are discussed in terms of the activation energies for vacancy-ion dissociation and ion transfer. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2015.07.057

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

In situ electrochemical impedance spectroscopy (EIS) was undertaken to investigate the contribution of a ferroelectric artificial solid electrolyte interface (SEI) to the enhancement of the rate capability of lithium ion batteries. Resistance elements, consisting of the cell reactions, the resistance of the electrolyte, R-sol, that of the Li metal anode reaction, R-Li, and the charge transfer resistance, R-ct, were measured. A small ferroelectric BaTiO3 (BT) load, similar to 1 mol %, notably reduced R-ct and R-sol compared with bare LiCoO2 (LC), indicating that loaded ferroelectric BT SEIs effectively promote Li inter/deintercalation into and from the active material, LC, and restrict cobalt ion dissolution into the electrolyte liquid. Lower R-ct and R-sol resulted in a significantly higher capacity retention ratio at a 10C rate compared with the initial cycle for small BT load, similar to 1 mol %. The capacity retention dropped rapidly, accompanied by a slight increase in R-ct for larger BT loads, 5 and 15 mol %, which may be attributed to the thicker BT layer and the existence of the impurity phase, BaCO3. These results imply that the ferroelectric SEI affected the kinetics of mobile Li ions at the cathode-electrolyte interface, significantly enhancing the rate capability. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.10NB02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The effect of quasi-millimetre-wave (24 GHz microwave) heating on creep deformation was investigated on partially-stabilised zirconia through tensile testing at temperatures from 1100 to 1350 degrees C over stresses from 5 to 10 MPa. The specimens were fabricated by sintering the 3 mol% of yttria stabilised ZrO2 (3YSZ) powder dispersed with SiO2, SiO2/SnO2 or SiO2/TiO2 at 1600 degrees C. In tensile test using the quasi-millimetre wave heating, strain rates of SiO2 dispersed 3YSZ were similar to that with a conventional furnace heating. The 3YSZ sample containing the TiO2 addition exhibited a different strain rate when heated by millimeter-wave irradiation as against conventional furnace heating, it is proposed that this difference can be explained due to TiO2 having a high-dielectric constant resulting in a non-thermal effect when subjected to quasi-millimeter wavelength radiation. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2015.01.006

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Language：English   Publisher：Institute of Physics  

The effect of Mg loading on the high-frequency tunable properties and dielectric loss of Ba<inf>0.8</inf>Sr<inf>0.2</inf>Ti<inf>1−</inf><inf>x</inf>Mg<inf>x</inf>O<inf>3</inf>(BSTM) ceramics was investigated. Variation in the lattice parameters and the 90° domain configuration with Mg loading indicated a decrease in the tetragonal distortion. Additionally, the 90° domain size decreased slightly with a low Mg loading, up to 0.1 mol %, resulting in a higher domain-wall density compared with the non-doped specimen. The 0.075 mol % Mg-loaded BSTM ceramic exhibited the highest tunability; this was attributed to the domain-size effect. The loss tangent (tan δ) roughly decreased with Mg loading, due to loaded oxygen vacancies. The maximum figure of merit value (FOM = tunability/tan δ) at 10 MHz was achieved for the 0.075 mol % Mg specimen, twice that of the non-doped specimen, due to an increase in the tunability and a decrease in the loss tangent with Mg loading.

DOI： 10.7567/JJAP.54.011502

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Ferroelectric barium titanate, BaTiO3 (BT) was coated on lithium cobaltate, LiCoO2 (LC), as an artificial solid electrolyte interface (SEI), via the simple sol-gel route. The high charge-discharge rate capabilities of the composite cathodes were evaluated up to 10C. The LC loaded with 1 mol% of BT had a measured capacity of 146 mAh/g, which was the highest value measured at 10C. This capacity was 78% of its initial value, and was 238% of the capacity of bare LC over the same number of cycles. (C) 2015 The Electrochemical Society. All rights reserved.

DOI： 10.1149/2.0041512eel

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The dependence of lithium ion conductivity on barium loading was investigated for Li0.33BaxLa0.56-2/3xTiO3 (LBLT, 0 &lt;= x &lt;= 0.1) ceramics. The highest bulk conductivity, sigma(dc), of 1.24 x 10(-3) S cm(-1) obtained for 0.25 mol.% Ba loading was slightly improved compared to that of non-doped Li0.33La0.56TiO3 (1.18 x 10(-3) S cm(-1)). The intensities of the XRD patterns in the independent cubic and tetragonal reflections, i.e., I-c(100) and I-t(101), were analyzed; a larger I-c(100)/I-t(101) ratio corresponded to a larger sigma(dc). A possible reason for the only slight enhancement of the sigma(dc) by a small loading of Ba is an increased volume fraction of the more highly conductive LBLT cubic phase. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2014.05.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The high charge-discharge rate characteristics of composite cathodes consisting of ferroelectric BaTiO3 (BT)-coated LiCoO2 (LC), synthesized via a simple sol-gel route, were evaluated, and the rate showed stepwise increases to as high as 5C. The LC-BT composite cathode annealed at 600 degrees C, LC-BT-600, notably retained high capacities, i.e., 122 mAh/g at 30 cycles, 5C and 99 mAh/g at 60 cycles, 5C. These capacities corresponded to 83% and 67% of the initial values and were as high as 158% and 245% of the capacities of bare LC over the same cycles, respectively. The ferroelectricity of the coated BT contributed to the improvement in high-rate performance. (c) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4898006

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Publishing type：Research paper (scientific journal)   Publisher：Trans Tech Publications, Ltd.  

We measured the microwave and millimeter-wave behaviors of ceramics and metal powders as a basis for developing microwave and millimeter-wave heating technology. In this study, nitride powders were subjected to microwave absorption measurements at elevated temperature. These measurements were performed using a system comprising a vector network analyzer, a circular wave-guide fixture, and a vacuum furnace. The sample’s microwave absorbency was evaluated by the change in reflection power from the sample in the circular wave-guide fixture under vacuum heating. Measurements were performed at approximately 24 GHz and at temperature up to approximately 1100°C. Boron nitride (BN) exhibited almost no absorption of microwaves up to 1100°C, similar to the results of a low-loss oxide powder such as alumina. Dichromium mononitride (Cr2N) powder exhibited a rather high absorption of microwaves at room temperature. During vacuum heating, absorbency of Cr2N started to decrease at 300°C, and became almost zero at temperature greater than 600°C, similar to the behavior of iron powder. This result indicated that roughly packed Cr2N powder absorbs microwave radiation; however, during vacuum heating, the compact body was sintered and the whole sample body became a reflector of microwaves. This change was irreversible, and the sample maintained its reflection behavior upon the cooling. When a mixed powder of Cr2N (20 mass%) and Al2O3 was heated under vacuum, the compact sample exhibited microwave absorption that increased with increasing temperature. This change was reversible upon cooling. These results indicated that the mixed powder did not become reflector of microwaves; Cr2N particles were not electrically connected each other because the Al2O3 particles kept the Cr2N particles separate during the vacuum heating process.

DOI： 10.4028/www.scientific.net/ast.88.31

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Under 24-GHz millimetre-wave irradiation heating ionic conductivity of zirconia base ceramics was up to 20 times higher than that of a conventionally-heated sample at the same temperature of 400 degrees C. The degree of enhancement could be altered by changing the stabilising atom from Y to Yb. Enhancement of ionic conduction was prominent in the setup condition of larger self-heating ratio and larger MMW absorbing materials. The isothermal improvement of ionic conductivity under MMW irradiation would be ascribed to the non-thermal effect. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2013.10.002

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The relationship between the optical phonon parameters and the oxygen ion conductivities were investigated for Al-Yb co-doped zirconia ceramics. Intrinsic intragrain ion conductivity, sigma(dc) decreased with increasing Al loading into ytterbia-stabilized zirconia, while the damping parameter of the lattice vibration, gamma(1TO), increased. This phenomenon agreed with findings of our previous study, which revealed a relationship between the sigma(dc), and the gamma(1TO) for zirconia-based ion conductors.

DOI： 10.4028/www.scientific.net/KEM.582.107

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The superplastically foaming method was adopted to make closed-pore inclusive zirconia-based ceramics. Lanthanum oxide was added to monoclinic or tetragonal yttria-stabilised zirconia to reduce the thermal conductivity of the matrix. Sintering and superplastic deformation led to a solid solution and transformation to the cubic phase. The resulting superplastically foamed porous ceramics having a porosity of 45% had only 40% of the thermal conductivity of the fully densified ceramics having the same composition. This value was comparable to that of conventionally fabricated porous ceramics with the same composition and porosity. The superplastically foamed ceramics had 60%, while conventionally fabricated ceramics had only 20%, of the mechanical strength of the fully dense ceramics. (c) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2013.05.084

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Language：English   Publishing type：Research paper (scientific journal)  

Ceramics of LaxSr1-xNbyTi 1-yO3 (LSNT) were synthesized under various reducing atmospheres. Covering the specimens with graphite carbon felt under an Ar-gas flow during sintering drastically enhanced the electrical conductivity, σ. Ti K-edge absorption spectra indicated the presence of Ti3+ for heavily reduced specimens. The increase in conductivity was attributed to the 3d band of Ti3+. The maximum value for the figure of merit, ZT, was obtained for strontium titanate ceramics modified with both 5 mol% La and 5 mol% Nb, namely 5/5-LSNT, exhibiting a ZT value of ~0.221 at 473 K. This high ZT value was almost 1.5 × larger than that of the conventional 10 mol% La-doped sample, 10/0-LSNT (ZT~0.144), and was mainly attributed to the larger Seebeck coefficient of the material. © 2013 The American Ceramic Society.

DOI： 10.1111/jace.12379

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Polarization contributions to the tunable properties of Ba0.8Sr0.2TiO3 ceramics were quantitatively studied by microwave measurements. The width of the ferroelectric domain walls (90 degrees domain walls) decreased with decreasing average grain size. The variation in domain size with grain size for grains smaller than 10 mu m was roughly proportional to the square root of the grain size, consistent with previous reports on BaTiO3. The smaller size of the 90 degrees domains (i.e., higher domain-wall density) resulted in greater tunability at an applied DC electric field of 6.7 kV/cm. The tunability of the specimen with a domain size of 161 nm was 26.5%, which was 4.4 times that of the specimen with a domain size of 259 nm (T = 6.0%). Under a relatively low DC field, the density of the domain-wall motion was the dominant factor determining the overall tunable properties, while the contributions of the ionic and electronic polarizations were relatively small in Ba0.8Sr0.2TiO3. (C) 2013 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.52.09KF06

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Lithium (Li) ion conductivities of Nd-doped (Li, La)TiO3 (LLNT) ceramics are evaluated as a function of Nd-loading. The bulk ion conductivity, sigma(dc), improves for the specimen with -0.75 mol% Nd. The conductivity of the 0.5 mol% Nd-loaded LLNT is sigma(dc) = 1.26 x 10(-3) S cm(-1) at room temperature. It is the highest conductivity measured, and is 1.33 times higher than that of the non-doped ceramic. The enhancement of the Li ion conductivity with Nd-doping in the LLNTs is attributed to an increase in the volume fraction of the A-site disordered cubic phase. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2013.04.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Interdiffusion between the perovskite CaTiO3 and SrTiO3 diffusion couple was investigated in an annealing method using 24-GHz MMW irradiation as the heating source. Interdiffusion was enhanced by MMW irradiation, and the apparent activation energy for interdiffusion decreased 54%, compared with conventional furnace heating. The intrinsic diffusions for both Ca2+ and Sr2+ were also enhanced, although their relative degrees of enhancement differed, partly as a result of differences in MMW absorptivity between the two ceramics. The observed isothermal diffusion enhancement could be ascribed to a nonthermal effect, apart from the differential degree of enhancement between the transport species. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2013.02.038

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

All contributions to the total conductivity, electrolyte electrode interfaces, grain boundaries, ion-hopping, and optical phonons, were determined on the 8 mol% yttria-stabilized zirconia (8YSZ) and 8 mol% ytterbia-stabilized zirconia (8YbSZ) ceramics using the wideband conductivity spectroscopy. Complex conductivity spectra from 10(-1) Hz to 10(14) Hz were successfully obtained. The higher total conductivity of the 8YbSZ ceramics compared to the 8YSZ in wideband frequencies as mainly attributed to difference in the DC conductivity due to universal dielectric response (UDR), sigma(dc); sigma(dc) ((8YbSZ)) &gt; sigma(dc) ((8YSZ)). Other parameters in the UDR and the optical phonon parameters did not greatly influence on the difference in their intrinsic conductivities.

DOI： 10.4028/www.scientific.net/KEM.566.141

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Porous ceramics incorporate pores to improve several properties including thermal insulation, maintaining inherent ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics are usually fabricated through an insufficient sintering, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foam only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. Based on this concept we fabricated 8mol% yttria stabilized zirconia based porous ceramics and examined the properties concerning the high temperature structural material with thermal insulation.

DOI： 10.4028/www.scientific.net/MSF.735.109

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Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

DOI： 10.2109/jcersj2.121.527

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Broadband dielectric spectra from 10 to 10(14) Hz were acquired for 8 mol. % Y2O3/Yb2O3-stabilized zirconia (8YSZ and 8YbSZ) ceramics that related the dipole and ionic polarization losses to the absorption efficiency of electromagnetic irradiation. For 24 GHz irradiation, 8YSZ exhibited a higher absorption efficiency than 8YbSZ, resulting in a higher dielectric loss. The difference in the dielectric loss was interpreted as the difference in the loss of the dipoles originating from the fluctuations in the defect associations (Y'(Zr)Vo and Yb'(Zr)Vo). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729147]

DOI： 10.1063/1.4729147

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.matlet.2011.12.066

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A unique micropore foaming technique was used to enhance the thermoelectric properties of polycrystalline aluminum-doped zinc oxide (AZO). Silicon carbide (alpha-SiC) and aluminum nitride (AlN) were used as foaming precursors. Thermoelectric conductivity, kappa, decreased on addition of both precursors, increasing the porosity. Electric conductivity, sigma, decreased upon addition of alpha-SiC, and subsequent addition of AlN reversed the effect. This phenomenon is due to the chemical reactions that occur upon addition of each precursor: the active oxidation of alpha-SiC and the decomposition reaction of AlN. The Seebeck coefficient, S, for 0.5 mol% AlN-doped AZO (Al0.005Zn0.995O, AZO-0.005) was more than twice that of conventional non-doped AZO. Accordingly, the power factor and the figure of merit, ZT, for the porous AlN-doped AZO-0.005 were 4.9 and 5.8 times those of the conventional polycrystalline AZO, respectively, demonstrating that the compositionally optimized porous AZO exhibited excellent thermoelectric properties at high temperatures.

DOI： 10.1111/j.1551-2916.2011.04837.x

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Language：Japanese   Publishing type：Research paper (scientific journal)  

We have already proposed and demonstrated novel ceramic foams named "superplastically foamed ceramics" utilizing the superplastic deformation. Since almost all the processes are carried out in solid phase, figure and the location of the foaming agent can be controllable, leading to desired patterning of closed pore in a fully densified ceramics. We have already demonstrated two-dimensional (2D) pore patterning through the superplastically foaming method. In the present study, we aim to fabricate helical tubular pore in zirconia based ceramics as a typical 3D patterned pore. As a foaming agent, SiC powders were used with a form of thin sheet based on methylcellulose aqueous solution followed by drying. A core cylindrical matrix compact was first fabricated using Φ 10 steel die and the liner foaming agent was attached to make helical pattern. The patterned core matrix was placed in Φ 14 or Φ 15 steel die and pressed together with the filled matrix powder. The resultant powder compact was heat treated at 1600°C for 8h for sintering followed by foaming to give a ceramics with 3D tubular pore. Continuous upheaval reflecting the tubular pore was clearly observed on the side wall of the cylinder and helical tubular pore with different pitch can be fabricated.

DOI： 10.2497/jjspm.59.90

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Broadband conductivity spectra from 100 to 10(14) Hz (100 THz) were acquired for yttria-stabilized zirconia (10 mol% Y(2)O(3)-doped ZrO(2), 10YSZ) to quantify contributions from conduction due to the electrolyte electrode interface, grain boundaries, universal dielectric response (UDR), and optical phonons. The UDR contribution governed the intrinsic conductivity at all frequencies except specific frequencies in the terahertz range, where phonon contributions governed conductivity for both ceramics and single crystals. UDR parameters sigma(0) and sigma(dc), increased with increasing temperature, resulting in increased microwave conductivity. The complex conductivity converged at frequencies of hundreds of gigahertz due to a decrease in the power-law constants, with increasing temperature. The optical phonon contribution to the total conductivity, due to an increase in the damping factor gamma(1TO) with increasing temperature, was small, while the phonon-mode frequency omega(1TO) affected the microwave conductivity of 10YSZ. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mseb.2011.09.039

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Language：Japanese   Publishing type：Research paper (scientific journal)  

The effect of reducing atmosphere on yttria dispersed AIN ceramics sintered by millimeter wave-HIP combined sintering was investigated. The specimens were sintered by millimeter wave (MMW) heating under nitrogen reducing atmosphere containing 3 vol% hydrogen followed by post-HIP treatment at 1700°C for 0.5 h under nitrogen pressure of 190 MPa. The relative densities to the theoretical one saturated at the first MMW heating over 1700°C. Thermal conductivities of AIN ceramics sintered by MMW heating under heavily reduced atmosphere with nitrogen were higher than that through MMW heating under normally reduced atmosphere. The thermal conductivity increased with decreasing the yttria additive amount and with increasing the sintering temperature. The optimized yttria dispersion amount was 1 wt% in the MMW heating at 1800°C for 0.5 h. Relative density and thermal conductivity increased by post-HIP treatment. The optimized yttria dispersion amount shifted from 1 wt% to 3 wt% after post-HIP treatment.

DOI： 10.2497/jjspm.59.17

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Complex conductivity wideband spectra from 10(-1) to 10(14) Hz (100 THz) were determined for 8 mol% yttria-stabilized zirconia (8YSZ) and 8 mol% ytterbia-stabilized zirconia (8YbSZ) ceramics. The contributions of electrolyte-electrode interfaces, grain boundaries, intragrain ion-hopping, and optical phonons were quantified to relate the microscopic conduction behavior to the overall conductivity. Intrinsic conductivity was mostly governed by ion-hopping. For both 8YSZ and 8YbSZ, ion-hopping followed the universal dielectric response (UDR) for broadband frequencies except for the phonon dispersion frequencies. The higher overall conductivities of the 8YbSZ ceramics compared to the 8YSZ ones were attributed to differences in the UDR contributions. The dominant factor determining the difference in the intrinsic conductivity in broadband frequencies from direct current (DC) to microwave between the 8YSZ and 8YbSZ ceramics was the DC conductivity due to UDR, sigma(dc), where sigma(dc(8YbSZ)) &gt; sigma(dc(8YSZ)). Other parameters in the UDR and the optical parameters did not greatly influence the intrinsic conductivities. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.011102

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Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.63.651

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Alumina/carbon-black composite ceramics with different percolation thresholds were fabricated by changing the size ratio of constituent particles. The dependence of resistivity on pressure was established for each sample. The compositional dependence of resistivity can be explained by percolation theory. The percolation threshold decreases with increasing alumina/carbon-black particle size ratio. The pressure dependence of the resistivity increases as the composition approaches the percolation threshold. When the relative composition at the percolation threshold is fixed, the sensitivity increases with increasing matrix/dispersoid initial particle size ratio. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2011.04.042

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Ionic conductivity in yttria-stabilized zirconia ceramics under millimeter-wave irradiation heating was compared with that obtained using conventional heating. The former was found to result in higher conductivity than the latter. Enhancement of the ionic conductivity and the reduction in activation energy seemed to depend on self-heating resulting from the millimeter-wave irradiation. Millimeter-wave irradiation heating restricted the degradation in conductivity accompanying over-substitution, suggesting the optimum structure that provided the maximum conductivity could be different between the two heating methods. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2011.01.017

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Language：Japanese   Publishing type：Research paper (scientific journal)  

With the aim to improve the thermal conductivity of yttria dispersed AIN ceramics through a short time and low temperature treatment under nitrogen atmosphere, millimeter wave (MMW) heating was combined with post-HIP treatment. Relative density increased by post HIP treatment over 1600°C on previously MMW heated samples even with the same temperature. The thermal conductivity exceeded over 170W/m°K when treated through MMW-HIP combined sintering with 1700°C+ 1700°C treatment by 0.5 h+0.5 h. This valued had been attained through the MMW treatment alone at 1800 °C for 2 h under 3 wt% hydrogen mixed nitrogen atmosphere. The optimal dispersion amount was 3 wt% in the MMW-HIP combined sintering while that was 5 wt% in the MMW sintering alone. The relative density has been saturated at the first MMW heating over 1700°C. On the other hand, thermal conductivity increased with the treatment temperature both in first MMW and post HIP. No significant pressure dependence can be seen in the thermal conductivity with this experimental condition.

DOI： 10.2497/jjspm.58.57

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Three-dimensional (3D) tubular cannels in fully densified zirconia ceramics have been fabricated by a newly developed solid-state free-foaming method using superplasticity. Three mole percent of yttria-stabilised zirconia (3YSZ) and alpha-SiC were used as foam matrix and foaming agent simultaneously. Dried pattern of 15 wt% (wt%) alpha-SiC slurry based on 10 wt% methyl cellulose buried into 3YSZ powder compacts and proper heat treatment at the sintering temperature causes successful fabrication of 3D cannel in zirconia ceramics. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2010.08.016

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Language：English   Publishing type：Research paper (international conference proceedings)  

Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent. © 2011 Ceramic Society of Japan.

DOI： 10.1088/1757-899X/18/18/182002

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.surfcoat.2010.08.017

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Alumina based closed pore dominated substrates have been fabricated by using superplastically foaming method developed by our group. Co-dispersing of magnesium aluminate spinel (Spinel) and zirconia without dopant (0YZ) provided adequate superplastisity to alumina matrix, while individual dispersion of spinel or zirconia resulted in only small deformation. The dielectric constant of superplastically foamed alumina decreased monotonically with porosity. Introduced pores were all closed nature at least up to 30% of porosity, at that porosity the permittivity became half as that of full dense one. Effect of the sweating water or ambient humidity has been proved to be identical to those of full dense one, which is favorable for semiconductor substrate. (C)2010 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.118.1090

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10832-009-9568-9

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Other Link： http://link.springer.com/article/10.1007/s10832-009-9568-9/fulltext.html

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

We have already innovated superplastically foaming method in which pore expands after densification of the matrix utilizing the superplastic deformation. Based on this superplastically foaming method using 3YSZ (3 mol% yttria stabilized zirconia) and alpha SiC as matrix and foam agent, respectively, we have successfully fabricated several dots closed pore pattern and C shaped as well as S shaped closed tube patterns by optimizing the amount of matrix 3YSZ. In addition to the shape of the closed pore, the protuberance based on the expansion of the pore changed with the location of the foam agent in the matrix. The shape of the closed pores and the interaction between them can be controlled by the concentration of the foam agent and the amount of the matrix.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

By using 24 GHz millimeter-wave irradiation, full densification of AlN added with Y(2)O(3) was attained at 1700 degrees C, which is comparable to 28GHz-wave irradiation. Thermal conductivity of a resultant sample exceeded 200 W/mK, which is the highest value in AlN fabricated in non-reducing atmosphere.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The basic mechanical properties of antiperovskite manganese nitride, Mn3Cu1-xGexN, known as an isotropic negative thermal expansion (NTE), have been evaluated. The mother material, Mn3CuN, was a soft and ductile intermetallic compound with a positive linear thermal expansion coefficient (alpha=+20 x 10-6 K-1) at room temperature. The thermal expansion properties of Mn3CuN were dramatically changed by Ge doping, resulting in an extremely large NTE material (alpha=-12.5 x 10-6 K-1) by 50% substitution of Cu with Ge. Associate with this, the mechanical properties were found to be strongly modified by Ge doping, and both the stiffness and the hardness of Mn3Cu1-xGexN increased with increasing the Ge content, x. The NTE material, Mn3Cu0.5Ge0.5N, had an enhanced hardness of 570-620 H-v and an exceptionally large Young's modulus of 211-320 GPa. The giant, isotropic NTE compatible with the enhanced value of Young's modulus enables us to fabricate extremely stiff, stable, and lightweight zero thermal expansion composites for the use in many fields of industries.

DOI： 10.1111/j.1551-2916.2009.03297.x

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

The applicability of several nitride powders for use as foaming agents in superplastically foaming ceramics was investigated. Ceramic mono-foams were fabricated successfully using AlN and Si3N4 foaming agents. By using BN as a foam agent, on the other hand, we cannot fabricated well developed ceramic foams due to cracking and fracture. When the quantity of foaming agent was increased, the porosity increased to a certain amount, then saturated. With equal amounts of Si3N4, the porosity from the dispersed foaming agent was higher than that obtained from a monolithic compact without mixing, which was similar to the case of SiC foam agent. (C) 2009 The Ceramic society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.1233

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

With the aim to reduce the permittivity of a dielectric substrate, closed pores have been introduced into alumina based ceramics by our innovated superplastisically foaming method. Affect of the ambient humidity on the dielectric constant was compared to those for conventional porous ceramics as well as full densified one. In the dry atmosphere, the dielectric constant (k) decreased with the porosity similar to the conventional porous ceramics. Affect of the ambient humidity on the dielectric property was almost identical to that of fully densified one. The degradation of mechanical strength depended on the pore size introduced. (C)2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.1013

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

The electrodeposition of silver was investigated with 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide containing Ag-TFSI at 150 degrees C. The influence of current density oil the morphology of the silver deposit was Studied by cyclic voltammetry and scanning electron microscopy. The size of the silver crystallite became smaller and dendrite-like growth was suppressed with increasing current density.

DOI： 10.5796/electrochemistry.77.645

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Magnesia-graphite composite ceramics were fabricated by hot pressing in Ar atmosphere, and their electrical properties were measured. The electrical resistivity increases as the graphite volume fraction x decreases, following well-accepted power law model based on the percolation theory. Renormalized pressure coefficient of resistance, d(In R)/dP, decreases as x decreases. This behavior can be explained by the strong enhancement of d(In p)/dx toward the percolation threshold. By fitting the x dependence or d(In rho)/dP with a theoretical equation, the Young's modulus of the composites was estimated. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.793

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Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

We have already innovated superplastically foaming method in which pore expands after densification of the matrix utilizing the superplastic deformation. Based on this superplastically foaming method using 3YSZ (3 mol% yttria stabilized zirconia) and α-SiC as matrix and foam agent, respectively, we have successfully fabricated several dots closed pore pattern and C-shaped as well as S-shaped closed tube patterns by optimizing the amount of matrix 3 YSZ. In addition to the shape of the closed pore, the protuberance based on the expansion of the pore changed with the location of the foam agent in the matrix. The shape of the closed pores and the interaction between them can be controlled by the concentration of the foam agent and the amount of the matrix.

DOI： 10.2497/jjspm.56.389

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Authorship：Lead author,　Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Ceramic monofoams based on titania were fabricated using superplastic deformation driven by the evolution of gas from a foam agent. Titania based polyfoam with porosities of up to 25% can be fabricated by dispersing only 1 mol% of foam agent (silicon carbide). When the mechanical strength of superplastically foamed titania was compared with that of fully densified titania and conventionally fabricated porous titania, the superplastically foamed ceramics retained 70% of the mechanical strength of the dense ceramics, while that of the conventional porous ceramic decreased to 40%. Niobium-doped semiconducting titania polyfoam was also fabricated. The electrical resistivity and affect of ambient humidity were similar to those of the dense ceramics. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2008.07.010

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Alumina-based ceramic foam utilizing the superplastic deformation after sintering has been proposed and demonstrated by the present authors. Effects of two kinds of additives, magnesia or magnesium aluminate spinel on the. figure of alumina-based ceramic foams were examined. In both cases, total porosity increased with increasing the addition amount up to 30 mol%. With the same addition amount, the porosity of spinel-added foam was slightly larger than that of magnesia-added one. On pore expansion, relative density of pore shell decreased while the density degradation degree of magnesia-added foam was more serious than that of spinel-added one. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2008.03.136

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adem.200800259

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL PUBLISHING, INC  

Alumina-graphite composite ceramics were fabricated by normal sintering in a reducing atmosphere, and their bulk resistivity measured. Because the composites consisted of connected clusters of conducting graphite particles within an insulating alumina matrix, the experimental results were discussed in terms of percolation theory. The electrical resistivity increases as the volume fraction of graphite (x) decreases, following a well-accepted power law model. The observed critical exponent was larger than the expected universal value based on a three-dimensional structure, due to a weighted distribution of conductivity throughout the sample. The renormalized pressure coefficient of resistance, d(ln R)/dP, decreased as x decreased and was explained by a strong enhancement of d(ln rho)/dx as the percolation threshold was approached.

DOI： 10.1111/j.1551-2916.2008.02820.x

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We have already fabricated ceramic mono-foams by expanding once-sintered dense shells utilizing the superplastic deformation of 3YSZ, 8YSZ, alumina and titania based ceramics. In the present study, granular coating method was applied to make a porous ceramics through the superplastically foaming method based on 3YSZ. Both mechanical strength and thermal conductivity were measured and compared with those of fully densified as well as conventional porous 3YSZ ceramics. Porous ceramics with porosity over 35% can be fabricated with less than 15 vol% of foam agent. The mechanical strength and thermal conductivity were superior or comparable to those for conventionally fabricated porous ceramics with the same porosity level.

DOI： 10.2497/jjspm.55.732

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The piezoresistance coefficient was measured on co-doped silicon carbide ceramics. Evaluation samples of alpha-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratios. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

DOI： 10.1016/j.ceramint.2007.09.033

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The influence of coarse powder on grain growth during hot isostatic pressing (HIP) was examined. Powder mixtures containing 0%, 0.5%, 5% and 20% coarse powder were prepared. The magnesia sintered without pressure was subjected to HIP at 1600 degrees C for 0.5 h at different pressures. The samples produced from fine powder had the largest grains after HIP treatment, although they had the smallest grains before it. The optical transparency of the HIP-treated magnesia ceramics increased with grain size. (c) 2007 Acta Materialia Inc. Published. by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2007.04.032

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

A new superplasticity foaming method was used to form zirconia-based ceramic foams. Silica and alumina were chosen as additives because they facilitate the 2D superplastic deformation. The effects of these additives on macroscopic pore evolution were examined after heat treatment for up to 40 h. The addition of silica or alumina also enhanced the 3D deformation during superplasticity foaming. The total porosity of mono-foams made from 3 mol% yttria-stabilised zirconia without additives increased with heat treatment for up to 24 h, and then levelled off. The porosity of silica-dispersed foam was greater than that without additives and continued to increase for up to 40 h. Conversely, the porosity of alumina-dispersed ceramic foam reached saturation within 8 h. Consequently, the porosity of alumina-dispersed foam was greater than that without additives after heating for 8 h, while the latter exceeded the former with prolonged heating for more than 16 h. The detailed effects of alumina dispersion on the foam development behaviour were examined in connection with the microstructure. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jeurceramsoc.2006-08-008

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Model ceramic foams were fabricated by expanding once-sintered dense shells utilizing the superplastic deformation of alumina dispersed with 3 mol% yttria-stabilized zirconia (3YSZ) or magnesia. The grain growth of aluinina was suppressed by adding 3YSZ and the resultant grain size and amount of dispersion were closely related to the total porosity. Total porosity of the ceramic foam depended on the grain size and their distributions irrespective of the size of starting powders. (c) 2006 Elsevier Ltd. All ri-hts reserved.

DOI： 10.1016/j.jeurceramsoc.2006.03.002

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The purpose of this study is to make a superplasticity ceramic foam with several isolated closed pores. Three mol percent of yttria stabilized zirconia (3 YSZ) was used as foam matrix and -SiC as foam agent. Two kinds of powder slurries based on methyl cellulose aqueous solution were first prepared. Using the 3YSZ slurry, green sheet was fabricated using a glass bar. After dried, patterning of SiC slurry was conducted on the 3YSZ sheet through a copper mask. Three patterned sheets were cut and buried in a 3YSZ powder compacts. Through the heat treatment at the sintering temperature, a ceramic foam containing several isolated closed pores derived from the SiC pattern was successfully fabricated.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Piezoresistance coefficient was measured at room and elevated temperatures on 6H-SiC ceramics doped with different amounts of boron, aluminum or gallium. The piezoresistance coefficient increased with increasing the addition within their solid solution limits. The profile of carrier concentrations, lattice constant and piezoresistance coefficient against doping levels were closely related. In few samples piezoresistance coefficient slightly decreased with measurement temperature. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mseb.2006.08.050

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Na beta-alumina is a two-dimensional ionic conductor in which insulating spinel layers separate conducting planes of Na+ ions. Na beta-alumina ceramics is expected to be used as solid electrolytes because it is strong ionic conductor and mechanically reliable. Therefore, we prepared c-plane-oriented Na beta-alumina ceramics from three aluminum sources using a hot-pressing method and evaluated their ionic conductivity and mechanical strength. In all samples, the ionic conductivity perpendicular to the pressing direction was ten times greater than in the parallel direction. The mechanical strength parallel to the pressing direction was 1.5 times larger than that in the perpendicular direction. The samples made from a mixture of 50 mol% platelike gibbsite and 50 mol% spherical alumina showed the maximum preferential orientation with favorable relative density.

DOI： 10.2109/jcersj.114.719

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/adem.200600070

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We employed Na beta-alumina ceramics as a candidate of structural material of which strength can be controllable. Mechanical strength of Na beta-alumina ceramics revealed to be enhanced up to 50% by ion exchange of Na+ by larger K+. Maximum mechanical strength was as large as 450 MPa that can be easily degraded by simple annealing at moderate temperature. Such large strength maintained on service could make it useful as structural material. Furthermore it is advantageous for recycling because it can be easily broken after annealing. The increase in mechanical strength on ion exchange was not dependent on the composition of beta-alumina but dependent on the internal stress developed due to the difference in the cation sizes. After showing maximum strength, prolonged ion exchange time leads to strength degradation due to the crack generation. When NaK-beta-alumina ceramics was used instead of Na beta-alumina, ion exchange time showing maximum strength and degree of strength degradation had been changed. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2005.12.033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

We evaluated the effect of high-voltage screening on thermally shocked titania ceramics. When the strength distribution was broadened by a thermal shock close to the critical temperature difference, high-voltage screening removed the relatively weak samples, and. when thermally shocked samples were mixed into pristine samples, all the thermally shocked samples were eliminated when adequate screening field was applied.

DOI： 10.1111/j.1551-2916.2005.00682.x

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Language：English   Publishing type：Research paper (international conference proceedings)  

Naβ-alumina is a two- dimensional ionic conductor in which conducting planes of Na+ ion are separated by insulating spinel block layers. For practical use, Naβ- alumina needs not only high ionic conductivity but also mechanical reliability. Therefore, we prepared preferentially oriented Naβ-alumina ceramics by hot pressing and evaluated the ionic conductivity and mechanical strength. The ionic conductivity perpendicular to the c-axis-oriented plane was five times higher than that parallel to c-axis. From the preferentially oriented Naβ-alumina ceramics three types of test pieces were cut for a three-point bending test. In one type of test piece, the longest side was parallel to the hot-pressing direction, while the longest sides were perpendicular to that direction in the other types of test pieces. The latter test pieces showed mechanical strength 1.5 times that of the former.

DOI： 10.4028/0-87849-982-2.147

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Language：Japanese   Publisher：The Surface Finishing Society of Japan  

The interfacial pH during Ni plating from the Watts bath was measured by using a rotating ring disk electrode system where the Sb-plated ring electrode acts as a pH sensor. It was clarified that a linear relationship exists between the electrode potential of the Sb-plated ring electrode and the pH in the range from 2.0 to 6.5 and was also clarified that the Sb-plated rotating ring electrode could be used as a pH sensor for the electroplating process in these pH ranges. The Ni-Al(OH)₃ composite film was electrodeposited by controlling current density under certain conditions, while the rise of interfacial pH during the plating process was estimated from the in situ pH measurement described above. The results of the SEM/EDX observations showed that minute particles, probably aluminum hydroxide, could be deposited with nickel from Al³⁺ contained in a non-turbid Watts bath under certain conditions determined by the interfacial pH measurement described herein.<br>

DOI： 10.4139/sfj.57.597

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The transparent magnesium-oxide (MgO) ceramic could be fabricated by a hot-isostatic press (HIP) technique of pressure less-sintered MgO compact, using non-agglomerated MgO powder with the average primary particle size of 57 nm. The relative density and average grain size of MgO compact pressureless-sintered at 1600 degrees C for 5 h were 96.7% and 10.7 mu m, respectively. owing to the HIPing operation (0.5 h) of pressureless-sintered compact at a temperature between 1500 and 1600 degrees C. relative densities of the MgO ceramics attained 99.9% or more with light transmission. The average grain size increased from 132 to 199 mu m with HIPing temperature from 1500 to 1600 degrees C. The in-line transmission of the MgO specimen HIPed at 1600 degrees C for 0.5 h increased from 52 to 55% with increasing wavelength from 500 to 900 nm and corresponded to approximately 65%, compared to that of the MgO single crystal. The thermal conductivity of this MgO specimen attained with increasing test temperature up to 873 K. 53.5 W m(-1) K-1, whereas the thermal diffusivity decreased gradually to reach 0.0416 cm(2) s(-1) 0 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jeurceramsoc.2005.06.011

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Evaluation samples of p-type α-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide with boron, aluminum, or gallium at various ratios. The resultant p-type silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter decreased with nitrogen doping pressure indicating that the incorporated nitrogen were dissolved into silicon carbide. In the case of boron and aluminum doped samples, the piezoresistive coefficient decreased with the nitrogen doping pressure, while gallium doped one remained almost constant with doping pressure.

DOI： 10.2497/jjspm.52.753

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Language：Japanese   Publishing type：Research paper (scientific journal)  

The electrodeposition of Cu-graphite composite film from copper sulfate bath containing graphite particle has been studied. The graphite particles were oxidized with nitric acid in order to introduce surface oxides. The role of the functional groups on the graphite edge during Cu-graphite composite plating was evaluated by the potentiometric titration method. The titration curve obtained in the presence of graphite particles and that without graphite particles crossed over each other at the pH 2.45 which is probably pKa of the compound in the presence of Cu 2+ in the bath. However, this value is found to be lower than the pH 3 in the same solution without Cu 2+ ion. This phenomena might be recognized by the adsorption of Cu 2+ ion on the functional group of the graphite at the pH higher than the pKa value. Upon analyzing the surface morphology of the Cu-graphite composite coating, it is found that the specific ordered structure of the coating can be fabricated by controlling the pH of the bath.

DOI： 10.2497/jjspm.52.619

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/j.1151-2916.1997.tb03026.x

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DOI： 10.1111/j.1151-2916.1999.tb02204.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

The change in strength of barium titanate/zirconia composite on polarization treatment is evaluated, and the mechanism of this phenomenon is discussed. We have already reported that the bending strength of this composite has increased on longitudinal poling. In this Study bending strength of BT/8YSZ composite increased on longitudinal poling and decreases on transverse poling compared with the untreated samples. Both strengthened and weakened specimens tend to return to the almost original strength by heating over Tc of barium titanate.

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DOI： 10.14852/jcersjsuppl.112.0.S1402.0

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Acoustic emission (AE) is very useful technique to understand the microfracture behavior in materials. However, it is difficult to monitor AE behavior in small or thin specimen compared with the size of transducer. Recently we developed the non-contact AE measurement system using laser interferometer for various applications, and it was successfully used to detect AE signals of ceramic coating materials during thermal cycle tests. Dielectric strength is a key property for dielectric ceramics such as barium titanate and titania, and it is very important to evaluate dielectric failure in these materials. However, conventional piezoelectric transducer could not be applied to this test. It is difficult to attach a transducer to specimen because thickness of specimen is thin compared with that of mechanical test, and conductivity through transducer is not desired for dielectric breakdown test. We successfully detected AE signals during dielectric breakdown test using laser interferometer. AE sources such as dielectric breakdown and partial discharge were also clearly identified by frequency and location analysis of AE waveforms.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

DOI： 10.1023/A:1024934807879

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Language：English   Publisher：The Ceramic Society of Japan  

Naβ-alumina is a two-dimensional ionic conductor in which conducting planes of Na + ion are separated by insulating spinel block layers. For practical use, Naβ-alumina needs not only high ionic conductivity but also mechanical reliability. Therefore, we prepared preferentially oriented Naβ-alumina ceramics by hot pressing and evaluated the ionic conductivity and mechanical strength. The ionic conductivity perpendicular to the c-axis-oriented plane was five times higher than that parallel to c-axis. From the preferentially oriented Naβ-alumina ceramics three types of test pieces were cut for a three-point bending test. In one type of test piece, the longest side was parallel to the hot-pressing direction, while the longest sides were perpendicular to that direction in the other types of test pieces. The latter test pieces showed mechanical strength 1.5 times that of the former.

DOI： 10.2109/jcersj.110.376

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Nabeta-alumina is a two-dimensional ionic conductor in which conducting planes of Na+ ion are separated by insulating spinel block layers. For practical use, Nabeta-alumina needs not only high ionic conductivity but also mechanical reliability. Therefore, we prepared preferentially oriented Nabeta-alumina ceramics by hot pressing and evaluated the ionic conductivity and mechanical strength. The ionic conductivity perpendicular to the c-axis-oriented plane was five times higher than that parallel to c-axis. From the preferentially oriented Nabeta-alumina ceramics three types of test pieces were cut for a three-point bending test. In one type of test piece, the longest side was parallel to the hot-pressing direction, while the longest sides were perpendicular to that direction in the other types of test pieces. The latter test pieces showed mechanical strength 1.5 times that of the former.

DOI： 10.2109/jcersj.110.376

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CERAMIC SOC  

Piezoresistivity effect of a silicon carbide-based ceramic fiber (Nicalon family) was evaluated when a single fiber was buried at the tensile plane in a plastic rectangular bar subjected to bending to apply a stable tensile strain. Electrical resistivity change during the bending was monitored by a digital high-resistance meter. From the fracture strain, Young's modulus, and the resistivity change, the piezoresistance coefficient is calculated to be 1.6 x 10(-11) m(2)/N, which is in agreement with the reported value for silicon carbide single crystals and our own reported value for polycrystalline silicon carbide ceramics.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Dielectric breakdown of titania ceramics was investigated with respect to the precurrent which is the current flow before breakdown. The precurrent behavior can be divided into two regions; an electron multiplication region in which carrier electron increases with a constant rate and a critical current increase just before the breakdown. Optical microscopic observation indicated that a part of titania ceramics melted during dielectric breakdown. Relation between critical current and applied electric field, as well as the electric power and heat calculated from the critical current, supported the observed melt of titania ceramics.

DOI： 10.2109/jcersj.109.1274_891

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

DOI： 10.1023/A:1010945320700

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

DOI： 10.1023/A:1006728227815

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

The change in strength of barium titanate/zirconia composite on polarization treatment is evaluated, and the mechanism of this phenomenon is discussed. We have already reported that the bending strength of this composite has increased on longitudinal poling. In this study bending strength of BT/8YSZ composite increased on longitudinal poling and decreases on transverse poling compared with the untreated samples. Both strengthened and weakened specimens tend to return to the almost original strength by heating over Tc of barium titanate. Then, the crack propagation after polarization treatment is observed by SEM, and the detour of cracks around barium titanate grains is found in the cracks going along the poling direction. The detour of crack probably has close connection with the increase in strength in the poling direction.

DOI： 10.1117/12.424423

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The change in strength of barium titanate/zirconia composite on polarization treatment is evaluated, and the mechanism of this phenomenon is discussed. We have already reported that the bending strength of this composite has increased on longitudinal poling. In this paper, poling time and applied electric field intensity are varied in order to elucidate the strengthening mechanism. Moreover, it is found out that the polarization strengthened specimen can be weakened to the almost original state by heating above T-c of barium titanate. Then, the crack propagation after polarization treatment is observed by SEM, and the detour of cracks around barium titanate grains is found in the cracks going along the poling direction. The detour of crack probably has close connection with the increase in strength in the poling direction. (C) 2000 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0955-2219(00)00110-2

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/j.1151-2916.2000.tb01403.x

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DOI： 10.1143/jjap.39.1193

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DOI： 10.2109/jcersj.108.1261_795

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

In situ monitoring of indentation cracking in dielectric ceramics was examined by introducing a semiconducting region in the surface of the ceramics. Titanium dioxide was employed as the dielectric ceramic. The monitoring sensitivity can be enhanced by controlling the thickness of the conducting layer.

DOI： 10.1023/A:1006758624648

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

The CuO/ZnO heterocontact is made by stacking CuO and ZnO porous ceramics and its catalytic activity for CO oxidation reaction is evaluated as a function of applied bias. Its catalytic activity is strongly depend on the dc applied bias and when the reverse bias (CuO-, ZnO+) is applied to the heterocontact, the amount of the produced CO2 from the catalytic interface rapidly increases, while it decreases when forward bias is applied. The magnitude of the enhancement of the catalytic activity by reverse applied bias is extremely large (30% for -2.0 V at 320 degrees C), comparing with the results in the gradient composition CuO/ZnO heterocontact. The p-i-n structure is suggested as to the electronic structure of the CuO-ZnO contact interfaces and supposing p-i-n structure, the surface Fermi level position of CuO and ZnO are guessed to move as a function of applied bias. The catalytic reaction over CuO make a large contribute to the whole catalytic reaction at the CuO/ZnO heterocontact and it would be modified by the applied voltage dependent surface Fermi level position of CuO. The working mechanisms of such phenomena are qualitatively discussed by the electronic theory of catalyst proposed by Wolkenstein.

DOI： 10.1023/A:1009910827420

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DOI： 10.1016/s0955-2219(99)00032-1

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DOI： 10.1143/jjap.38.l662

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Pore size of several porous materials such as zeolites (MCM-41 and MCM-48) and highly fined grain aggregates of zirconia was estimated by means of positron annihilation lifetime measurement. Observed lifetimes of ortho-positronium (over similar to 20 ns, tau(4) and tau(5)) correspond to the meso-pore sizes assessed by conventional porosimetries due to a nitrogen physisorption and a mercury porosimetry. The long-lived lifetime components included an unassigned lifetime component (tau(5)), which was not detected by the other porosimetry. The observed ortho-positronium lifetimes are correlated to the mean size of pores. A relation between relative intensities of the long-lived ortho-positronium components (I-4 and I-5) and specific surface areas is discussed and a variation of a numerical concentration of pores is correlated to the change of the particle sizes of the zirconia aggregates.

DOI： 10.2109/jcersj.107.123

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DOI： 10.1016/s0167-2738(98)00264-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

The effects of high voltage screening on mechanical strength distributions obtained through three different bending tests of ceramic materials were examined. Cumulative failure probability was calculated using the mean rank method. There is a stress gradient at the bottom face of the bending sample, leading to a positional dependence of stress concentration at a specific shape flaw.

DOI： 10.1023/A:1006673722467

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

Propagation of indentation fracture was firstly monitored on alpha-SiC ceramics through a current drop accompanied by the decrease in current conduction area. The current decrease ratio before and after indentation during the constant voltage application was proportional to the crack area formed. However, during the indentation, the current anomalously increased even though the indentation crack propagated. This phenomena is probably due to the piezoresistance effect which has already reported in SiC single crystal. When bending stress was applied to alpha-SiC ceramics, the current increase ratio was proportional to the bending strain. A fracture foreseeing system is proposed for alpha-SiC ceramics in which initial crack monitoring without stress application and bending strain monitoring utilizing the piezoresistance effect are combined. (C) 1999 Kluwer Academic Publishers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

This paper is devoted to the study of the piezoresistance of conducting composite thin films consisting of epoxy resin and needle-like conductive fillers. The surface resistivity of the thin films at room temperature depended on filler volume fraction and relative humidity (rh). The effect of moisture absorption on the piezoresistance of the composite thin films was studied under various rh values. At high rh values, strain dependence of resistance was positive, and this positive coefficient decreased with decreasing rh value. At 30%rh, it became negative and its absolute value increased with decreasing rh. These results suggest that the piezoresistance effect of the conducting thin films is enhanced by moisture absorption by the epoxy matrix that is relatively hydrophilic. From these observations, the piezoresistance effect is considered to be based on the following two strains: one is derived from a mechanical stress and the other is due to environmental stress induced by moisture absorption.

DOI： 10.1143/jjap.37.l1158

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

The surface resistivity of crosslinked polymer matrix conductive ceramic filler composite thin films was studied as a function of composition and temperature. Epoxy resin and unsaturated polyester resin were selected as the insulating matrices. The resistivities of both thin films showed a percolative conduction, and the critical percolation threshold values of the filler weight fraction depended on the type of insulating polymer. The epoxy composite film exhibited a pronounced positive-temperature-coefficient-of-resistivity (PTCR) effect above the glass transition temperature of the matrix. In contrast, the unsaturated polyester composite did not show such an effect. To examine the nature of the percolation and the resistivity versus temperature behavior, the adhesive strength measurements and thermomechanical analysis were conducted on the matrix polymers. The results suggest that the percolation behavior and the occurrence of the PTCR effect in conductor-filled crosslinked polymer composites can be more precisely calculated by taking into account the thermomechanical interaction factor of the components.

DOI： 10.1143/jjap.37.l1190

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DOI： 10.1016/s0167-2738(98)00086-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Cubic zirconia base ceramic composites were fabricated by dispersing barium titanate with various contents. Mechanical strength increased on longitudinal poling and decreased on transverse poling. This strength change has been interpreted as being related to internal stresses generated at the matrix/dispersant interface.

DOI： 10.2109/jcersj.106.537

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Electrochemical Society Inc.  

The CuO/ZnO heterocontacts for carbon monoxide (CO) gas sensors were made using CuO ceramics with different histories, and their gas sensing characteristics were evaluated. The CuO/ZnO heterocontact made by the quenched CuO sintered compact showed enhanced CO and CO2 gas sensitivity, while that made by slowly cooled CuO showed no selective CO gas-sensing characteristics with no CO2 gas sensitivity. The quenched CuO ceramics were thermodynamically stable but the slowly cooled ones were not
therefore the adsorbed CO molecules on the quenched CuO are thought to be stable and have longer lifetimes. The specific reaction between the adsorbed CO on CuO and adsorbed oxygen on ZnO would be promoted by long lifetime adsorbed CO on CuO and that may be the origin of the enhanced CO gas sensitivity of the quenched-CuO/ZnO heterocontact. The concentrations of cation vacancies of the quenched CuO ceramics can be controlled by controlling the firing temperatures. However, when the CuO ceramics for the CuO/ZnO heterocontact were made by firing and quenching, the ability to be selective in CO gas sensing of the heterocontact was not easily controlled by the control of the defect concentrations of the CuO ceramics.

DOI： 10.1149/1.1838315

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A phenomenon was discovered that leads to the selective detection of abrupt increases in the temperature of conductive composite thin films consisting of conductive ceramic fillers and an insulating polymer matrix. Examining the heating rate dependence of the positive-temperature-coefficient-of-resistivity (PTCR) effect provided information about this intelligent phenomenon. The anomalous PTCR effect was observed above 0.3 °C min-1 for all the prepared films. However, the magnitude of the anomaly decreased when the heating rate decreased below 0.1 ° Cmin-1, and when the heating rate further decreased below 0.04 °C min-1, the anomalous resistivity-temperature relationship disappeared. The results suggest that these thin films can selectively detect abrupt increases in temperature, which could lead to an intelligent mechanism. Our results also suggest a PTCR mechanism, in which the expansion of crosslinked polymers in the thermodynamic nonequilibrium state essentially produces the anomaly. © 1998 American Institute of Physics.

DOI： 10.1063/1.122880

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1006696419446

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Netherlands  

DOI： 10.1023/A:1006552832241

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Netherlands  

Hardened gypsum is chosen as a simple model of hardened cement materials and an analogy between the mechanical and dielectric strength distributions is investigated. Both of the strengths are evaluated in terms of Weibull statistics and a two-parameter Weibull function is adopted for both of the strength distributions. Both plots show good coincidence which is independent of the water content used during the mixing of hemihydrate gypsum powder for hardening. The hardened gypsum sheets made with 70 wt % of water, have mechanical and dielectric strength distributions that show two different behaviours in the Weibull plots, however, both the plots agree with each other. From our results, it is concluded that the mechanical strength distribution of hardened gypsum can be evaluated in terms of the dielectric strength distribution, which can be easily measured from a breakdown test.

DOI： 10.1023/A:1018579216679

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Mechanical and electrical properties of zirconia-based alumina composites as solid electrolyte used in solid oxide fuel cells (SOFC) were examined, in which the alumina addition and its morphology were changed. The bending strength increased with the addition of 0.38 mu m alumina up to 30 mol%, then decreased. In this sample the ionic conductivities almost remained constant up to 30 mol%.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Screening fields, at or below which 10%, 30% and 50% of TiO2 ceramic samples would break electrically, were applied to samples which show single-mode strength distribution. After these high-voltage screenings, the surviving samples were subjected to mechanical strength measurement and the resultant strength distributions were compared with the original distributions. This high-voltage screening was also applied to model ceramics samples composed of titania with two different relative densities. The effect of high-voltage screening and the correlation between mechanical and dielectric strengths are discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

The surface properties of copper oxide (CuO) were discussed for considering the working mechanism of a CuO/ZnO heterocontact gas sensor having carbon monoxide (CO) gas selectivity. We focused on p-type semiconducting CuO, using sodium as a dopant, which is a key material for selective CO gas sensing and its surface properties were characterized by XPS, TPD and FT-IR analyses. It was found that the Cu/O ratio of the 1 mol% Na2CO3-added CuO surface was higher than that of pure CuO surface by XPS analysis. By TPD analysis, it was found that CO was adsorbed more strongly on 1 mol% Na2CO3-added CuO than on pure CuO. By the in situ IR measurement of CO adsorbed on the surface of 1 mol% Na2CO3-added CuO specimen under 300 degrees C, we found two asymmetric bands of CO, whereas an asymmetric streching CO2 band was found on IR measurement of pure CuO specimen. It was confirmed that Cu atoms on pure CuO surface exposed to CO at 300 degrees C changed from Cu2+ to Cu1+ or Cu-0, in contrast to Cu atoms on 1 mol% Na2CO3-added CuO surface, which changed to Cu2+. The electrical conductivity was measured as a function of temperature for pure CuO, CuO with 1 mol% Na2CO3 and ZnO specimens. The resistivity of ZnO was larger than that of pure CuO and CuO with 1 mol% Na2CO3 by three and six orders of magnitude at 250 degrees C, respectively. A working mechanism of CuO (Na)/ZnO heterocontact gas sensor was elucidated in order to explain its high CO selectivity.

DOI： 10.2109/jcersj.104.415

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Language：Japanese   Publisher：The Ceramic Society of Japan  

Single crystals of (Ba_<0.96-x>Ln_xSr_<0.04>)TiO_3 (Ln=La, Gd) were grown over a composition range of x=0.001 to 0.03. Electrical resistivities of the single crystals were measured by the DC four-probe method. The temperature dependence of resistivities of these crystals changed from semiconductive to metallic at the Curie temperature (T_C). Although the room temperature resistivities of Gd-doped single crystals were independent of Gd concenration of 1 to 3%, they decreased monotonically with increasing the dopant concentration after annealing in a reducing atmosphere.

DOI： 10.2109/jcersj.104.273

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Other Link： https://jlc.jst.go.jp/DN/JALC/00370916307?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Single crystals of (Ba(0.96-x)Ln(x)Sr(0.04)) TiO3 (Ln=La, Gd) were grown over a composition range of x=0.001 to 0.03. Electrical resistivities of the single crystals were measured by the DC four-probe method. The temperature dependence of resistivities of these crystals changed from semiconductive to metallic at the Curie temperature (T-C). Although the room temperature resistivities of Gd-doped single crystals were independent of Gd concentration of 1 to 3 %, they decreased monotonically with increasing the dopant concentration after annealing in a reducing atmosphere.

DOI： 10.2109/jcersj.104.273

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Electrochromism of Prussian blue (PB) involving proton insertion/extraction was investigated in an aqueous HCl solution using a Ta2O5·nH2O/PB laminate, formed by spin-coating a peroxo-polytantalate solution on an electrodeposited PB film. Reversible and stable electrochromic performance was observed with more than 10000 repeated coloring and bleaching cycles, demonstrating that the film of Ta2O5·nH2O serves as a proton-conductive protecting layer to prevent PB from dissolving in a strong acid solution. Insertion behavior of proton into the PB framework is compared with those for K+, Rb+ and Cs+ by means of a cyclic voltammogram and equilibrium potential measurements. The equilibrium potentials measured as a function of the degree of intercalation have shown that the maximum accommodation of proton is 3.0 (per Fe3+4[Fe11(CN)6]3 unit), which is in agreement with K+ and Rb+. However, the potential-composition curve observed with the PB-proton system is quite different from others not only in the potential range but also in shape, featuring by a conspicuous inflection at the middle region of the intercalation level. The intercalation behaviors are also discussed using a lattice statistical model.

DOI： 10.1016/0167-2738(95)00226-x

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Language：English   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

A simultaneous loading system in which fracture stress distribution was substituted by fracture time distribution was previously proposed. However, this method could only be applied to electroconductive materials. In the present study, application of this simultaneous loading system was attempted on insulating materials to which electrical conduction was introduced. A thin gold him is coated on titanium dioxide ceramics to introduce electrical conductivity in them. The average strength and the Weibull modulus were not affected by the conductive coating. It is concluded that our simultaneous loading system can be used in the evaluation of dielectric ceramics and the equivalent strength distribution is obtained.

DOI： 10.2109/jcersj.103.730

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DOI： 10.1016/0167-2738(95)00068-h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Electrical and mechanical properties of ceramic composites were investigated in order to establish a fracture prediction technique. Ceramic composites consist of calcium fluoride as an insulating matrix and silicon carbide as electrically conductive additives. An electrical conduction path was formed by adding more than 4 vol% of SiC additives in the composites and the fracture strength increased by the increase of SIC additives. By applying mechanical load, electrical resistance of the composites increased up to fracture under tension while did not change or slightly decreased under compression. The changes in electrical resistance were suggested to occur by the change of connectivity of conduction path in the composites. These results suggest the possibility of predicting fracture in ceramic composites.

DOI： 10.2109/jcersj.103.576

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An alternative method to obtain a strength distribution of many test pieces simultaneously has been proposed. In this method, the bending stress of all subjected samples is simultaneously increased by utilizing their elastic modulus constancy, and the fractured sample number is monitored by the change in electric conductance. Copyright © 1995, Wiley Blackwell. All rights reserved

DOI： 10.1111/j.1151-2916.1995.tb08649.x

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A screening field at or below which 30% of TiO2 ceramic samples break electrically was applied to the samples. After high‐voltage screening, the surviving samples were subjected to mechanical strength measurement and the resulting strength distribution was compared to the original distribution. The effect of high‐voltage screening and the correlation between mechanical and dielectric strength are discussed. There is a correlation between mechanical and dielectric strengths with a correlation coefficient of 0.77, which indicates the validity of high‐voltage screening. Copyright © 1995, Wiley Blackwell. All rights reserved

DOI： 10.1111/j.1151-2916.1995.tb08648.x

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Soc of Japan  

The effect of high voltage screening on ceramics parts composed of titania ceramics with relative densities of 60 and 90%, was examined. Before screening, strength distribution was clearly discriminated into two regions, high strength region and low strength region. The dielectric strength was measured on the low strength samples, and the electric field below which all of the low strength parts would break was estimated as a screening field. After electric screening, the mechanical strength was measured and compared with the original one. Ceramic parts composed of only high strength region were obtained by eliminating the low strength parts electrically.

DOI： 10.2109/jcersj.103.1090

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Amorphous tungsten trioxide thin films were prepared using a rf magnetron sputtering method. The relation between structure and electrochromic properties was investigated. At the macroscopic level, the films had dense structures. From Raman spectroscopic and X-ray radial distribution analyses, it was deduced that the networks were basically formed by three-, four- and six-membered rings of corner-sharing WO6 octahedra, and in the films with low O/W atomic ratios many edge-sharing units were present. It was also found that the films with high O/W ratios showed good electrochromic properties, which were closely related to the six-membered rings. © 1994.

DOI： 10.1016/0022-3093(94)90290-9

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/0013-4686(93)e0003-5

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Peroxo-polymolybdotungstates are formed by the direct reaction of a mixture of metallic Mo and W (for example, 5:5 mixture) with hydrogen peroxide solution. A homogeneous and amorphous thin film (0.4 microm, typically) is fabricated on an ITO glass substrate by spin-coating using such a solution. After heat-treatment at 120°C, it exhibits electrochromism excellent in both reversibility and response time in an organic Li-electrolyte. The film colored at -1 V (versus Ag/AgCl) shows rather flat absorption spectrum. Its color is dark grayish blue and the ΔOD between -1 and +0.5 V reaches 0.7 at 670 nm (λmax). Kinetic aspect of such electrochromic films will also be dicussed. © 1994.

DOI： 10.1016/0167-2738(94)90385-9

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Language：English   Publishing type：Research paper (scientific journal)  

Two kinds of solid state ECD prototypes were fabricated by combining electrochromic films and a Ta2O5·nH2O proton conducting film. Electrochromic characteristics of these devices were comparable to those using liquid electrolyte. We also demonstrated reversible EC characteristics of Prussian blue with insertion and extraction of proton, using a Ta2O5·nH2O film. © 1994.

DOI： 10.1016/0167-2738(94)90329-8

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Electrochemical intercalation of Li into hexagonal- and pyrochlore-type cesium tungstates (CsyW1-y/6O3
y=0.3 and 0.5, respectively), and their bronzes (CsyWO3) derived from cesium peroxo-polytungstates was investigated in a 1M LiClO4/PC. Intercalation characteristics of those compounds are discussed in relation to their structures. © 1994.

DOI： 10.1016/0167-2738(94)90148-1

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A very smooth amorphous molybdenum oxide thin film can be fabricated easily by a spin-coating technique using a solution of peroxo-polymolybdic acid, which is formed by the direct reaction of metallic molybdenum with hydrogen peroxide, Amorphous MoO3 • n H2O resulting from heating such a film at 80-150°C exhibited reversible electrochromism in an organic electrolyte solution. However, its electrochromic characteristics depended on the heating temperature. Coloration dynamics of films treated at various temperatures were investigated by a potential step method. When the film was treated at temperatures as high as 150°C, its coloration process was diffusion controlled, while the transient current observed with films treated at lower temperature did not obey the Cottrell-type relationship. Such behavior is discussed in relation to the structural features of the amorphous MoO3 • n H2O films. © 1994, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2054850

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE PUBL B V  

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DOI： 10.1016/0167-2738(93)90028-2

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We have derived theoretical forms of the transition current to be induced when an electrochemical cell consisting of a solid electrolyte and an intercalation-type electrode is driven by an external source of a constant voltage, for both cases that the kinetics is controlled by the charge transfer and by the diffusion. Experimental data taken with a solid state cell, Li| polymer electrolyte|WO3, ITO, are analyzed on these bases. The results demonstrate that chrono-amperometric analysis can be successfully performed using such a cell without a reference electrode. © 1993.

DOI： 10.1016/0167-2738(93)90256-3

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Peroxo-polytungstic acid, formed by the direct reaction of metallic tungsten with hydrogen peroxide, precipitated an amorphous salt with potassium bromide. Decomposing the precipitate at 400-800°C in air yielded white hexagonal potassium tungstate, KxWO3+ x 2 (x=0.3), with lattice parameters of a=7.31 and c=7.65 Å. On the other hand, thermal decomposition in a reducing atmosphere (H2/H2O) at 500°C gave dark blue hexagonal tungsten bronze (HTB), KxWO3, with a=7.38 and c=7.52 Å, which were almost identical to those reported for HTB. It was found that the redox reaction between tungstate and HTB was completely reversible. A porous pellet of the present HTB showed metallic conductivity (≈10 S/cm, at 25°C) under dry conditions. In a wet atmosphere with only slight humidity, however, its conductivity was dramatically reduced. The conductivity was recovered by treating it again in a dry condition. © 1993.

DOI： 10.1016/0167-2738(93)90052-5

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Thermal decomposition of cesium peroxo-polytungstate, an amorphous precursor, yielded not only pyrochlore-type but also hexagonal WO3-type cesium tungstate, depending on the Cs/W ratio (x) in the precursors
the former is in the range 0.48 ≤ x ≤ 0.54 and the latter 0.30 ≤ x ≤ 0.34. Mixtures of these two phases were formed in the intermediate region of x. On reduction at 700°C, the pyrochlore phase gave a compound with the same framework, with its cubic cell parameter being elongated from 10.25 to 10.32 Å, but reoxidation resulted in a mixture of pyrochlore and hexagonal phases. In contrast, reduction and oxidation of the hexagonal phase at 600°C was reversible. Powder XRD profile refinements were performed with reduced and oxidized hexagonal cesium tungstates (x = 0.30) in the space group P 63/mcm. The former compounds (a = 7.4049(1) and c = 7.6098(1)) are based on an almost idealized h-WO3 framework with Cs sitting on its large 2b interstices (Rf = 0.0240). The oxidized compounds (7.4012(18) and 7.6728(17)Å Rf = 0.007) possessed a lacunar tungsten sublattice. © 1993 Academic Press, Inc.

DOI： 10.1006/jssc.1993.1090

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Peroxo polytungstic acids are promising inorganic resist materials which become insoluble in water by UV irradiation. After UV irradiation, part of oxygen molecules, decomposition product of the peroxo groups, was stably caged in the amorphous network. This mechanism is discussed in connection with the densification of thin films during UV irradiation.

DOI： 10.2109/jcersj.101.143

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/nikkashi.1993.1041

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Tantalum and niobium based amorphous solids were prepared by drying respective peroxo polyacids. Peroxo-polytantalate (Ta-IPA) was obtained by a direct reaction of Ta(OC2H5)5 with H2O2, and its Nb-analogue (Nb-IPA) was synthesized by dissolving metallic Nb in H2O2. Niobium carbide also gave a pale yellow solution (Nb-IPA) with H2O2, which had carbon incorporated as a hetero atom. Alternating current electrical conductivity measurements were carried out with pellet samples. Each specimen showed similar temperature dependency indicating its proton conductive mechanism was the same. The conductivity of Ta-IPA solid was larger than those of the others (e.g. 3.9×10-6 S cm-1, 27°C). Conduction mechanisms are discussed i relation to the water content and the structure of these materials. © 1992.

DOI： 10.1016/0167-2738(92)90282-T

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A hexagonal form of WO3 (a = 7.3244(6), c = 7.6628(5), Å, z = 6) was synthesized by the low temperature sintering of an ammonium peroxo-polytungstate precursor. This compound, the N/W ratio of which is 0.015 at most, is not identical to reported hexagonal WO3 from WO3 ·1/3H2O because its c-axis is significantly shorter than that of the latter (7.798 Å). Powder, XRD profile refinements were performed in the space group P63/mcm. We found two kinds of structural models that showed reasonably good profile agreement (R0.07). Both models are built up of remarkably distorted WO6 octahedra, in which part of the O-O distances are very short (2.32 ≈ 2.42, Å). Electrochemical intercalation of lithium into the present WO3 framework was investigated using a Li|LiPF6|WO3 cell. It was found that Li was intercalated reversibly up to the composition Li1.0WO3. © 1992 Academic Press, Inc.

DOI： 10.1016/S0022-4596(05)80292-0

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Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/oubutsu1932.61.266

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/0040-6090(91)90486-H

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/0013-7944(91)90253-w

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DOI： 10.1016/0167-2738(90)90149-l

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DOI： 10.1016/0167-2738(90)90072-y

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DOI： 10.1007/bf01107462

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Other Link： http://link.springer.com/article/10.1007/BF01107462/fulltext.html

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

Mechanical strengths of porous BaTiO_3 thick films were measured after dielectric breakdown , the bending stress was applied to the position where the electric field had been applied. Comparison of the Weibull plots of mechanical strength between electrically failed and unfilled (as-sintered) specimens has shown that no damage due to dielectric breakdown occurred and that the poling process naturally involved in the dielectric strength measurement increased the mechanical strength. Mechanical strength before dielectric breakdown was estimated by taking into account this strengthening effect which depended on the poling voltage, time and temperature. A clear correlation between mechanical and dielectric strengths was obtained with the correlation coefficient of 0.73.

DOI： 10.2109/jcersj.96.847

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

Mechanical and dielectric strength were measured for three types of BaTiO_3 thick films prepared under the different processing conditions. In any case, Weibull moduli for both strength distributions were identical in each type of films, though they differed among three types. The results indicated that dielectric strength measurement is a promising alternative method to distinguish the structural reliability change as influenced by processing parameters before firing within the framework of the same fabrication method .

DOI： 10.2109/jcersj.96.954

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Last author,　Corresponding author  

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J-GLOBAL

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J-GLOBAL

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Last author,　Corresponding author  

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Language：English   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

Web of Science

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Language：Japanese  

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Authorship：Lead author,　Corresponding author  

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Authorship：Lead author,　Corresponding author  

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Language：Japanese   Publishing type：Book review, literature introduction, etc.  

By using 24 GHz millimeter-wave irradiation, a full densification of AlN with the addition of Y2O3 was attained at 1700°C, which is comparable to 28 GHz-wave irradiation. Thermal conductivity of thus obtained sample exceeded 200 W/(m+K), which is the highest value among AlN-based ceramics fabricated in non-reducing atmosphere. The full densification was also reached at 1700°C in the Yb2O3 added AlN, which temperature was higher than that for 28 GHz-wave irradiated ceramics by ca. 100°C.

DOI： 10.2497/jjspm.56.377

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Language：Japanese  

Model ceramic foams were fabricated by expanding once-sintered dense shells utilizing the superplastic deformation of 8 mol% yttria-stabilized zirconia (8YSZ) dispersed with silica, titania or alumina. Similar to the case without dispersoid, 8YSZ based ceramic foam could not be fabricated with any amount of alumina addition. By adding silica more than 20 mol%, ceramic mono-foam can successfully be fabricated. The porosity increased with the sintering time up to 24 h, then saturated at about 40%. The porosity also increased with the amount of silica addition. In the case of titania addition, porosity was smaller compared with the same amount of silica addition.

DOI： 10.2497/jjspm.54.740

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese  

Evaluation samples of α-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratio. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure.

DOI： 10.2497/jjspm.53.876

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Language：Japanese  

Evaluation samples of α-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratio. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure.

DOI： 10.2497/jjspm.53.876

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Piezoresistance coefficient was measured by changing the addition of alumina +yttria or aluminum into silicon carbide ceramics. In the case of liquid phase sintering aids (alumina + yttria), piezoresistance coefficient is almost independent of the amount of sintering aids from 1 to 20 wt%. The piezoresistance coefficient increases with increasing the aluminum addition within its solid solution limit. Temperature dependency of piezoresistance coefficient is large in silicon carbide with large amount of aluminum addition.

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Language：Japanese   Publisher：Japan Radioisotope Association  

Effect of plasticization on free-volume hole size observed by means of positronium lifetime measurement was studied. Glass transition temperature significantly decreased with an increase of dioxane content while free-volume hole size increased Temperature dependence of the excess free-volume hole size by addition of dioxane was examined Hole formation energy E^Ps_H for the excess free-volume was estimated on an assumption of a Boltzmann type distribution. As the result, estimated value of E^Ps_H well agreed with those for several polymer systems previously obtained by means of heat capacimetry.

DOI： 10.3769/radioisotopes.51.60

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Piezoresistance coefficient was measured by changing the addition of alumina +yttria or aluminum into silicon carbide ceramics. In the case of liquid phase sintering aids (alumina + yttria), piezoresistance coefficient is almost independent of the amount of sintering aids from 1 to 20 wt%. The piezoresistance coefficient increases with increasing the aluminum addition within its solid solution limit. Temperature dependency of piezoresistance coefficient is large in silicon carbide with large amount of aluminum addition.

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Language：Japanese   Publisher：シ-エムシ-  

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Language：Japanese   Publisher：公益社団法人 日本化学会  

セラミックスの自己修復の例を解説した。セラミックスの自己修復では原子レベルの構造変化, ミクロンオーダーの組織変化, あるいは外場による制御を伴うミクロおよびマクロな構造変化を考えることになる。加熱により傷が縮小するクラックヒーリング, 亀裂の進展を相転移のエネルギーにより吸収する部分安定化ジルコニア, 分極方向に強度が増加する圧電粒子分散複合体について説明した。

DOI： 10.20665/kakyoshi.49.3_132

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