Effects of sintering temperature on sensing properties of WO(3) and Ag-WO(3) electrode for NO(2) sensor

Pure WO(3) and Ag-WO(3) (mixed solid solutions Ag with WO(3)) have been successfully synthesized by sol-gel method and the influences of calcination temperature on the particle size, morphology of the WO(3) and Ag-WO(3) nanoparticles were investigated. Powder X-ray diffraction results show that the hexagonal to monoclinic phase transition occurs at calcination temperature varying from 300°C to 500°C. SEM images show that calcination temperature plays an important role in controlling the particle size and morphology of the as-prepared WO(3) and Ag-WO(3) nanoparticles. The NO(2) gas sensing properties of the sensors based on WO(3) and Ag-WO(3) nanoparticles calcined at different temperatures were investigated and the experimental results exhibit that the gas sensing properties of the Ag-WO(3) sensors were superior to those of the pure WO(3). Especially, the sensor based on Ag-WO(3) calcined at 500°C possessed larger response, better selectivity, faster response/recovery and better longer-term stability to NO(2) than the others at relatively low operating temperature (150°C).