The Effects of Nano In2O3 and ZnO on the CO Gas Detection of the SnO2 Sensor

The pellet-type SnO2 sensor was synthesized by the solid state method and the effects of additives such as nano ZnO (1-12 mol %) and nano In2O3 (1-10 mol %) on the CO gas sensitivity of sensor were investigated. The optimum sintering temperature was chosen 800°C because of the porosity content of the samples. The phase analysis and microstructure of the samples were studied by x-ray diffraction and scanning electron microscopy, respectively. Results show that the electrical resistivity variations of the samples with time increased by increasing the amount of additives up to the optimum value for each additive. These optimum values were 10 and 7.5mol% for nano ZnO and nano In2O3, respectively. The best sensitivity and recovery and response times were obtained in the co-doped sample containing 10 mol% nano ZnO and 7.5 mol% nano In2O3. The higher values of the additives decreased the sensitivity of the samples due to the formation of undesirable phases.