n-type semiconductive oxides such as SnO₂ and ZnO have been used in the gas sensor applications. The change in the material conditions under an operating condition was investigated with respect to the optical and electric properties. The optical absorption between 300-600 nm was enhanced when a thin-film of SnO2 was exposed to 0.5 % H₂-N₂ gas at 300 deg.C, whereas such absorption change was not observed in ZnO up to 400 deg.C. While the change of the electric conductivity depended on the change in both carrier density and mobility in SnO₂, that in ZnO was mainly due to mobility change. Difference between SnO₂ and ZnO was detected in the response against 0.5 % H₂/N₂.

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Catalytic combustion sensors are widely used for detection of various combustion gases, however the sensing ability deteriorates due to catalyst poisoning by their incomplete combustion. In this study, the effect of UV illumination on the sensing ability of Pd/Pt co-loaded TiO2 thin film as a catalytic combustion sensor was investigated. The sensitivities to methanol and ethanol were increased by UV illumination. Therefore, the photocatalytic removal of surface organic substances by TiO₂ can enhance the combustion reaction on the Pd/Pt catalyst.

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Human breath includes many kinds of volatile organic compounds (VOCs). Parts of the VOCs have been regarded as biomarkers of diseases. It has been reported that breath of lung cancer patients includes nonanal whose concentration is ppb level. SnO₂-based gas sensors, one of the semiconductor-type sensors, have advantages of simple and real-time monitoring of VOCs-concentration. Conventional SnO₂-based gas sensors possess low sensitivity to aldehydes and aliphatic compounds. Therefore, the sensitivity of SnO₂-based gas sensors should be improved for detection of ppb-level-nonanal, which consists of aldehyde and saturated methylene chain groups. In this study, we investigate to optimize the amount of noble metal-addition and thickness of films for SnO₂-based gas sensors as nonanal sensors.

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Cuboid WO3 particles were prepared by precipitation method and hydrothermal synthesis. Sensing properties of the cuboid WO3 film sensor to dilute NO2 were studied. Temperature dependence on the sensing properties and effects of interference gases were investigated. Practical evaluation of the WO3 film sensor at roadside atmosphere was carried out and it was demonstrated that the measurement values obtained by the present sensor unit had equivalent accuracy and resolution with CLD detection without any maintenance and calibration for 10 weeks.

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We studied oxygen diffusion in BaTiO3 ceramics. In this study, we focused on the Ho concentration dependence of oxygen diffusion phenomena. The concentration of Ho in BaTi3 is in the range of 2x1018 - 6x1019 /cm3. Moreover, we will report the results of oxygen diffusion in Sm doped BaTi3.

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An electrode composed of BiCuVOx and perovskite type oxide was attached to NASICON solid electrolyte, and the interface was applied as a sensor for detecting organic gas. The gas sensor operated at 400-500 oC showed fairly good sensing properties to alcohol and aldehyde. It was found that the sensor response increases with decreasing the thickness of composite oxides electrode, indicating that the interface between composite oxide electrode and NASICON solid electrolyte plays an important part as a reaction place.

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Murata Mfg. has been producing co-fired multilayer piezoceramics commercially. Various applications of devices such as sensors, actuators and transformers had been developed so far. Multilayered piezo structure reduces driving voltage as well as acoustic or mechanical energy loss on the boundary of layers. It also enables vibration mode controlling with geometric arrangement of inner electrodes. In this report, several categories of multilayered piezoceramic devices will be overviewed.

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Optimization of Film Thickness and Material Design in Piezoelectric Thin Film Actuator

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Recent crystal growth of refractory crystals will be presented.

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This presentation deals with crystal growth and surface processing of low dimensional materials. There are many characteristic problems in the growth of two dimensional materials such as transition metal dichalcogenides and graphite, and one dimensional materials such as transition metal trichalcogenides. Surface processing and chemical modification are very important for the application of graphene - one atomic layer carbon material. We discuss the growth of nanowires as comparison with crystal growth of low dimensional materials.

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Rod-like Al-doped ZnO particles (Al/Zn = 0 and 2.0 mol%) were prepared by hydrothermal method. The electrical conductivities of the sintered pellets prepared from the rod-like Al-doped ZnO, rod-like ZnO, and commercial ZnO powders were investigated. The electrical conductivities of Al-doped ZnO sample was the highest in the samples. It was suggested that the sintered Al-doped ZnO pellets possessed preferred orientation, resulting in the increase of the electrical conductivity.

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Changes in the thermoelectric properties of multinary-doped ZnO were investigated particularly focusing on the thermal conductivity. Binary doping of ZnO with Al and Cu significantly reduced the thermal conductivity of the oxide, whereas the electrical conductivity was strongly deteriorated. Formation of CuAl2O4 spinel phase was suggested to be responsible for both enhanced phonon scattering and reduced carrier concentration. Ternary doping of ZnO with Al, Cu, and Ga resulted in high dimensionless figure-of-merit of ZT = 0.58 at 1238 K due to the reduced thermal conductivity and improved electrical conductivity.

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We have to explore new thermoelectric materials to realize our newly proposed PV/TE hybrid generators to harvest electricity from solar energy with high conversion efficiency. Three kinds of novel thermoelectric nanomaterials we are developing now will be chosen and their interesting features in terms of solar energy harvesting will be presented. Significance of "synergistic nanostructuring" concept is emphasized and we'll discuss how it can be achieved.

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The LixMnyTizNi1-y-zO2 (0 < x < 1.0; 0.5 < y < 1.0; 0 < z < 0.25) prepared from the corresponding sodium compounds via Li/Na ion-exchange. The powder X-ray diffraction measurement, ICP-AES chemical analysis, electron microscope observation, charge-discharge test were carried out. The precursors, NaxMnyTizNi1-y-zO2 (0.5 < x < 1.0; 0.5 < y < 1.0; 0 < z < 0.25), were calcined at 773 K for 12 h in air. After ion-exchanged, they were a characteristic of the broad X-ray peaks which were consistent with O3-type structure. When the Ni content was 0.15 apfu, the discharge capacity was higher than that of 0.05 and 0.10 apfu.

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Effect of Ca-doping on the ionic conductivity of LiSi2N3 was studied. The compositions of Li1-2xCaxSi2N3 (x=0-0.2) were synthesized by the reaction of Li3N, Si3N4, and Ca3N2 at temperature of 1873K-2073K. Ca was incorporated into the LiSi2N3 host lattice and formed the solid solution, Li1-2xCaxSi2N3. Activation energy for ionic conduction was decreased and ionic conductivity at room temperature was enhanced by Ca doping. At 298K, the ionic conductivity of densified Li1-2xCaxSi2N3 (x=0.075) ceramics achieved 1.6☓10-5Sm-1, almost 4 orders of magnitude higher than that of densified Li1-2xCaxSi2N3(x=0) ceramics (3.1☓10-9Sm-1).

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