MICROSTRUCTURE EVOLUTION AND GAS SENSITIVITIES OF PD-DOPED SNO2-BASEDSENSOR PREPARED BY 3 DIFFERENT CATALYST-ADDITION PROCESSES

We have investigated three ways of impregnating PdO on an SnO2 gas sen sor to achieve a simple and reliable sensor-fabrication process. These impregnating processes are: (1) coprecipitation of SnO2 and Pd compou nds in the solution; (2) addition of PdCl2 to SnO2 gel, followed by pr ecipitation; and (3) infiltration of PdCl2 into calcined SnO2 powder. Processes (1) and (2) introduce Pd into SnO2 particles before particle growth is completed. The phase and microstructures of particles have been analysed by X-ray diffraction, scanning and transmission electron microscopes, and an energy-dispersing X-ray spectroscope. The presenc e of Pd in the process of SnO2 precipitation restrains the growth of S nO2 particles and enhances a uniform distribution of fine PdO powder o n the SnO, grains. SnO2 gas sensors have been fabricated and tested fo r response to CH4, C2H6 and CO. Processes (1) and (2) show many possib ilities of improving SnO2 gas-sensor sensitivity with a simplified fab rication process.