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Characteristics for CO2 sensing of a CuO-based oxide capacitor were studied. The capacitances of CuO mixed with BaSnO3, SrTiO~, CaTiO3, and ZnO are dependent on the CO2 concentration, similar to CuO-BaTiO2. In particular, the mixed oxide, CuO-SrTiO3, is more sensitive to CO2 than CuO-BaTiO3, but requires a rather long time to recover. On the other hand, the mixed oxide capacitor, CuO-BaSnO3, exhibits high CO2 sensitivity, and a monotonic and approximately logarithmic relationship exists between the sensitivity and the concentration of CO2 from 100 ppm to 50%. Furthermore, the capacitance of CuO-BaSnO3 increased rapidly within 30 s after exposure to 2% CO2, and returned rapidly to the original level after reexposure to air. Therefore, the system, CuO-BaSnQ is promising for sensing COz over a wide range of concentrations. From a complex impedance measurement, the equivalent circuit of the sensor element can be expressed by a series connection of three parallel resistors and capacitors which correspond to the intragrain region, grain interface between CuO and BaSnO~, and electrode interface. Since exposure of the element to 2% CO2 varied the capacitance of the grain interface, the grain interface between CuO and BaSnO3 has an important role for CO2 detection.

An oxide capacitor consisting of BaTi03 and an oxide is studied as a new type COz sensor based on capacitance change. Sensitivity to COz, as well as the optimum operating temperature, was strongly dependent on the particular oxide mixed with BaTi03. Among the elements investigated in this study, CuO-BaTi03 exhibited the highest sensitivity to COz. In particular, the CuO-BaTi03 mixed oxide at the equimolar composition is highly sensitive to C o t . The optimum operating temperature and frequency for CuO-BaTi03 are 729 K and 100 Hz, respectively, and the 80% response time to 2% COz is within 25 s. The equimolar mixture of CuO and BaTi03 can measure the COz concentration from 100 to 60000 ppm. Carbonation of oxide seems to play a key role for the detection of C 0 2 on these mixed oxide capacitors. The optimum operating temperature of these mixed oxide capacitors for C 0 2 detection, therefore, correlates with the decomposition temperature of the carbonate corresponding to the oxide mixed with BaTi03. The capacitance increase of CuO-BaTi03 upon exposure to COz seems to result from the elevated height of the potential barrier at the grain boundary between CuO and BaTi03. Carbonation of CuO in the element seems to bring about the elevation in the height of the potential barrier. [

The electrophoretic deposition (EPD) method was applied for the preparation of yttria-stabilized zirconia (YSZ) films for a solid oxide fuel cell (SOFC). Dense YSZ films with uniform thickness can be readily prepared by EPD method. When the planar SOFC was fabricated by using La0.6Sr0.4MnO3 as a cathode and electroless plating Pt as an anode, the open circuit voltage and the maximum power density attained were 1.03 V and 1.87 Wcm−2, respectively.

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