Effects of sintering temperature on sensing properties of WO3 and Ag-WO3 electrode for NO2 sensor

Pure WO3 and Ag-WO3 (mixed solid solutions Ag with WO3) have been successfully synthesized by sol-gel method and the influences of calcination temperature on the particle size, morphology of the WO3 and Ag-WO3 nanoparticles were investigated. Powder X-ray diffraction results show that the hexagonal to monoclinic phase transition occurs at calcination temperature varying from 300 degrees C to 500 degrees C. SEM images show that calcination temperature plays an important role in controlling the particle size and morphology of the as-prepared WO3 and Ag-WO3 nanoparticles. The NO2 gas sensing properties of the sensors based on WO3 and Ag-WO3 nanoparticles calcined at different temperatures were investigated and the experimental results exhibit that the gas sensing properties of the Ag-WO3 sensors were superior to those of the pure WO3. Especially, the sensor based on AgWO3 calcined at 500 degrees C possessed larger response, better selectivity, faster response/recovery and better longer-term stability to NO2 than the others at relatively low operating temperature (150 degrees C).