Ni-GDC (gadolinia-doped ceria) composite powders, the anode material for the application of solid oxide fuel cells, were prepared by a solution reduction method using hydrazine. The distribution of Ni particles in the composite powders was homogeneous. The Ni-GDC powders were sintered at 1400˚C for 2 h and then reduced at 800˚C for 24 h in 3% H2. The percolation limit of Ni of the sintered composite was 20 vol%, which was significantly lower than these values in the literature (30-35 vol%). The marked decrease of percolation limit is attributed to the small size of the Ni particles and the high degree of dispersion. The hydrazine method suggests a facile chemical route to prepare well-dispersed Ni-GDC composite powders.

WO3-doped SnO2 thin films were prepared in a solution-deposition method and their gas-sensing characteristics were investigated. The doping of WO3 to SnO2 increased the response (Ra/Rg, Ra: resistance in air, Rg: resistance in gas) to H2 substantially. Moreover, the Ra/Rg value of 10 ppm CO increased to 5.65, whereas that of NO2 did not change by a significant amount. The enhanced response to H2 and the selective detection of CO in the presence of NO2 were explained in relation to the change in the surface reaction by the addition of WO3. The WO3-doped SnO2 sensor can be used with the application of a H2 sensor for vehicles that utilize fuel cells and as an air quality sensor to detect CO-containing exhaust gases emitted from gasoline engines.

A sensor element array for combinatorial solution deposition research was fabricated using LTCC (Low-temperature Co-fired Ceramics). The designed LTCC was co-fired at 800˚C for 1 hour after lamination at 70˚C under 3000 psi for 30 minutes. SnO2 sol was prepared by a hydrothermal method at 200˚C for 3 hours. Tin chloride and ammonium carbonate were used as raw materials and the ammonia solution was added to a Teflon jar. 20 droplets of SnO2 sol were deposited onto a LTCC sensor element and this was heat treated at 600˚C for 5 hours. The gas sensitivity (S = Ra/Rg) values of the SnO2 sensor and 0.04 wt% Pd-added SnO2 sensor were measured. The 0.04 wt% Pd-added SnO2 sensor showed higher sensitivity (S = 8.1) compared to the SnO2 sensor (S = 5.95) to 200 ppm CH3COCH3 at 400˚C.