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Various alkali niobate and barium titanate (BT) system ceramics were prepared using conventional sintering method, and their dielectric properties were measured. In this study, as alkali niobate, potassium niobate (KN), sodium niobate (NN), potassium sodium niobate (KNN) and lithium niobate (LN) were used. As the results, KN-BT and KNN-BT system ceramics showed almost flat temperate dependence of dielectric constants from 20 to 400 ˚C.

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Due to high remanent and excellent polarization fatigue characteristic, Bi₄Ti₃O₁₂-based ferroelectric materials are expected to be applied for lead-free piezoelectric material and devices. In this study, we synthesized (Bi,RE)₄(Ti,Mo,Si)₃(O,F)₁₂ (RE=La,Nd) and investigated their properties, crystal structure and ferroelectric performances. It was confirmed that P_r increased and dielectric loss decreased by substituting Mo and F, or adding BSO. Crystal structure analysis indicates that spontaneous polarization tend to be resulted from distortion of the perovskite layer. It is also suggested that Mo-substitution and BSO-addition have a significant effect on the perovskite layer.

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In our previous work, we focused on SrBi₂(Ta,Nb,M)₂O₉(M=W,Mo)-based sample and Bi₂SiO₅-added ones, and examined their ferroelectric performances and crystal and electronic structures. As a result, it was found that all the synthesized samples had the same structure as SBT, and SrBi₂ (Ta,Nb,Mo) ₂O₉-based sample showed higher Pr than SrBi₂(Ta,Nb,W)₂O₉. It was also clarified that Bi₂SiO₅-addition affected the ferroelectric properties.

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The transient response method is a useful technique for characterization of piezoelectric ceramics driving under high power condition. The conventional theoretical equation used in this method can not describe the change in frequency and beats. These phenomena cause from the nonlinear behaviors and give the material constants uncertainness. In this study, we characterized piezoelectric properties with taking their non-linear behaviors in account, based the electrical transient response technique.

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First-principles density functional calculations have been performed for a novel polar oxide ZnSnO3 with LiNbO3 (LN) type structure that was synthesized by high-pressure condition. The pressure dependence of the phase stability for Zn2+-Sn4+-O2- ternary system was computed through the calculations of bulk modulus, and we succeeded to reproduce qualitatively the phase transition to LN-type ZnSnO3 phase at high-pressure region. In addition, spontaneous polarizations and Born effective charges for ZnSnO3 was calculated by Berry phase approach, and the obtained results were compared with the electric properties of LiNbO3. The results indicated strong ionic character for Zn2+ and Sn4+ ions, indicating the difference of chemical bonding character and polarization properties between ZnSnO3 and LiNbO3 even with the same crystal structure

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A new garnet type lithium ion conductor, Li₇La₃Zr₂O₁₂ is expected as an electrolyte for 'All Solid State Battery'. We prepared Li₇La₃Zr₂O₁₂ at moderate temperature by Sol-Gel Method in order to suppress the volatilization of lithium at high temperature. Two types of structure are found, the tetragonal and cubic ones. The tetragonal form transforms to cubic one by absorbing CO₂ at lower temperature.

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Charge compensation mechanism in tin oxide (SnO2) films was investigated by characterization of SnO2 films grown by pulsed laser deposition aiming to achieve controlling of conductivity and surface reactivity for chemical sensor applications.

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CeO2 films were prepared on Al2O3 substrates by laser chemical vapor deposition at different laser power (PL) up to 182 W. The (100)-oriented CeO2 films were prepared at PL = 101 - 167 W (Tdep = 792 - 945 K). The texture coefficient (TC) of (200) reflection had a maximum of 6.7 at PL = 113 W (Tdep = 836 K). The (100)-oriented CeO2 films prepared on Al2O3 substrates consisted of granular grains and showed a columnar structure in cross section. The deposition rate of (100)-oriented CeO2 films showed a maximum of 43 umh-1 at PL = 152 W (Tdep = 912 K).

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We have investigated gas sensing properties of cerium oxide using A.C. impedance technique. The impedance analysis generally can divide d.c. resistance to three type contributions, R = Rb + Rgb + Rei, where R, Rb, Rgb, and Rei are d.c. resistance, bulk resistance, grain boundary resistance, and electrode interface resistance, respectively. In the case of cerium oxide, bulk resistance dominates the whole resistance response to odor gases.

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Recently, a high-performance gas sensor which can detect flammable gases such as H2, alcohols with high sensibility is required. The size of such sensor has to be small, either. In this study, in order to fabricate a combustion type small gas sensor with good response to the flammable gases, the titania thin films loading Pd and Pt fine particles were prepared on a glass capillary by using a sol-gel and a subsequent photo deposition process. The property and the sensibility against H2 and alcohol gases of the obtained titania thin films were examined.

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Nano-grained thermoelectric ceramics of n-type SrTiO₃ were fabricated from a La-doped nanocrystalline SrTiO₃ powder. Heat transport properties were examined by analyzing the heat capacity, thermal diffusivities, speed of sound, and the phonon mean free path. Electrical properties including electrical conductivity and Seebeck coefficients were investigated. It was observed that the thermal conductivity was much reduced, while the electrical transport behavior was similar to those of conventional micro-grained ceramics, for which the detailed mechanisms will be report in the presentation.

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Thermoelectric, TE, of thin-film and thick-film accelerate the development of various new TE microdevices. In this study, TE thin films have been deposited by sputtering and their TE properties measured at high temperature. The TE measurement for various thin film TE materials including Si, SiGe, Al doped ZnO, InO-ZnO, Nb doped SrTiO3 thin films have been studied.

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In order to fabricate the breakdown low voltage varistors, effects of Ba add ZnO varistors on the grain size of ZnO are investigated. Grain growth of ZnO can be notably promoted by adding both Ba and Bi. It is speculated that in adding both Ba and Bi to Mn-Co-added ZnO varistor, it is necessary to form molten phase of Ba and Bi to promote grain growth of ZnO and the growth of ZnO grain is not promoted due to the lack of coexistence of Ba and Bi because Ba formed compound with Mn independently for small addition of Bi.

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Needle-like TiN/Si3N4 composites were fabricated at 24 MPa at 1850 degree-C for 1h in N2 using hot-pressing. Needle-like TiN particles were synthesized by nitridation of TiO2 nanofiber obtained from TiO2 at KOH under hydrothermal condition. The influence of mixing state of starting powders on fabrication of needle-like TiN/Si3N4 composites was investigated.

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Microwave heating properties of a solid state sintered SiC and a reaction bonded SiC were studied. A multi mode microwave furnace at 2.45GHz with maximun 6kW input was used. Temperature rising rate of the solid state sintered SiC was faster than that of the reaction bonded SiC. And maximum temperature of the solid state sintered SiC was higher than that of the reaction bonded SiC.

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Engineering ceramics needs high resistance to damage .The objective of this study is to propose a novel concept for arresting propagation of surface rack. Ceramics with some roughness surface was prepared by machining process. Surface cracks at a convex part did not attenuate mechanical properties.

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Impact damages of pressureless sintered boron carbide ceramics were evaluated using a SUS304 plain plate (15mm square) or a SUJ2 sphere (4mm diameter) as a projectile. The result showed that the pressure of boron carbide ceramics generated by impact loadings were lower than those of other ceramics. This suggests that the pressureless sintered boron carbide ceramics makes it easier to convert the kinetic energy of projectile into the kinetic energy of ceramic debris formed during impact loadings.

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High density β-eucryptite ceramics was prepared using high purity and fine amorphous silica, α-alumina and lithium carbonate powders via the solid state reaction route.ß-eucryptite formation for the starting raw material mixture goes to completion at 950°C. Accordingly, the mixture was calcined at 900°C , ground, compacted and conventionally sintered at 1090°C or flux-sintered at 1020°C. Their relative densities reach 92 % and 99%, respectively. Their thermal expansion coefficients ( from RT. to 800°C) are 0.28×10^-6 and 1.2×10^-6, respectively. The dielectric constant of flux-sintered sample is 5.5 with loss tangent of 7.5×10^-3. These properties are found suitable for substrate materials to micro-electronic applications.

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Oxidation and/or corrosion behaviors of glass-like carbons (GLCs) in H₂SO₄, HNO₃ and in H₂O₂ aq at 70^oC were investigated with SEM, XPS and by measuring relative weight changes for 7 days. H₂SO₄ oxidizes C atoms at the GLC surface up to C-OH, while HNO₃ removes C atoms by further oxidation into the bulk forming cracks. H₂O₂ quickly removes surface C atoms to form large cavities.

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