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Layer-structured ferroelectric bismuth titanate (BiT) has attracted much attention as a promising material for Pd-free piezoelectric devices and RRAM. Since the spontaneous polarization (P_s) vector lies away from the a axis to the c axis by about 4-5 deg, P_s appears along the c axis (P_s(c)) as well as along the a axis (P_s(a)). Although the elucidation and the control of domain structures of ferroelectrics are crucial in view of their practical applications, the domain structure of BiT still remains unclear. We have observed the three-dimensional domain structures by scanning probe microscope (SPM) as well as the domain dynamics induced by electric field with optical microscopy. SPM observations revealed that the domains induced by P_s(c) are formed in P_s(a)–related 90-deg domains. Optical observations of interference colors enabled us to determine the directions of P_s(a) in 90-deg domain dynamics. P_s(c) domain dynamics were investigated by viewing interference colors in the a-b plane of tilted crystals.

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Desification mechanism of ceramic powder at room temperature on Room Temperature Impact Consolidation(RTIC) of Aerosol Deposition will be reported. The plastically deformation and reduction of submicron ceramic particle in starting powder were observed by a compression testing for a single ceramic particle.

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The nano-crystalline BaTiO3 have been successfully synthesized by mechanical alloying methods. The 6-8nm sized crystalline Perovskite particle were formed by room temperature reactions from SrO and TiO2.

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BaTiO₃-(Bi_1/2Na_1/2)TiO₃ solid-solution ceramics were developed as lead-free PTC materials. We have synthesized Ba_1-x(Bi_1/2Na_1/2)_xTiO₃ (abbreviated as BBNT100x: x=0-0.9) ceramics and measured the temperature dependence of resistivity. By sintering in N₂ flow atmosphere with low partial oxygen pressure, BBNT6-30 ceramics displayed PTC properties with the switching temperature of 130-210 ^oC and low resistivity at room temperature.The BBNT ceramics are the leading candidates of environmental friendly PTC thermistor materials.

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From environmental protection point of view, our newly developed "Wide-range high-temperature thremistor" has been widely used for exhaust gas sensor in the automotive industry. In this development, material design using first-principles calculations played an important roll for understanding of stability against heat and oxidizing/reducing atmosphere.

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To prevent the hazard problem in environment, we investigated Pb free solder for electronic ceramic parts. Sn-3Ag-0.5Cu alloys were selected as a general solder alloys, however, this alloy have the problem of electrde leaching for soldering electro ceramic parts. We investigate concentrate metal element at the interface between solder alloy and electrode in lead free solder. As a result, we found that the additives such as transition metal concentrate at the interface, prevent electrode leaching. Cu in Cu6Sn5 intermetallic compound were substitued the additive elements. The stable interface generated by this substitution prevent the electrode leaching.

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Recently, novel energy generation systems utilizing hydrogen or organic gases such as a fuel cell are widely investigated. In order to achieve them in practical use and to increase their applicability and safety, a development of gas sensors which are able to detect flammable gases with high response and accuracy is necessary. In this study, titania thin films which were co-loading platinum and palladium fine particles were prepared by wet chemical processes. This thin film showed the change of electro conductivity with high responsibility and concentration dependence against air-diluted hydrogen gas of less than 20%.

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Silicon nitride/tungsten compound composites were fabricated under hot press conditions. Tungsten boride addition did not affect the friction coefficient under hydrodynamic lubrication region, but the running in distance decreased with increasing WB content under water lubrication.

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So far as the authors know, there is no comprehensive study about the role of several kind of informations on fracture of ceramics. In this study, the role of fractue data such as strength data, fracture origin data, fracture location data, flaw-size data, and flaw-orientation data on the strength reliability analysis is theoretically analysed.

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Nanoindentation technique can be utilized for the mechanical property evaluation of visoelastic materials such as biomaterials and polymers. Indentation load-relaxation is more suitable for the measurement of the viscoelasticity than creep indentation utilized conventionally because of its mechanical simplicity. Our aim of this study is to develop a novel inverse analysis of the indentation load-relaxation of visoelastic materials, which does not depend on the contact mechanics. In this presentation, the effect of creep parameters such as the creep constant and creep stress exponent on the relaxation will be discussed.

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The high temperature plastic flow in polycrystalline oxide ceramics such as Al₂O₃ and TZP is very sensitive to small level of doping by various cations. High-resolution transmission electron microscopy observation and nano-probe energy-dispersive X-ray spectroscopy analysis revealed that dopant cations tend to segregate along the grain boundaries. The dopant effect is caused by change in the chemical bonding state in the vicinity of grain boundaries segregated with dopant cations. The electronic structure in the vicinity of the grain boundaries is one of the critical factors to determine the high temperature plasticity in oxide ceramics.

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