ULTRAFINE SNO2 PREPARED BY SUPERCRITICAL-FLUID DRYING TECHNIQUE (SCFDT) FOR GAS SENSORS

A sol-gel process, followed by supercritical fluid drying (SCFD) was e mployed to prepare ultrafine tin oxide. Two different procedures were introduced and the powder properties of these two products were measur ed and compared, including the particle size, specific surface area an d pore size distribution. Because the same reactive mechanism occurs i n the gas sensing process and catalytic process, the sensor properties can be improved largely by the use of ultrafine tin oxide. In this pa per, different gas sensing properties were observed when the two produ cts were used as base materials of gas sensors. The effects of pH valu e on the pore structure and response (reversion) time of the sensors a re also discussed.