Effects of sintering temperature on sensing properties of V2O5-WO3-TiO2 electrode for potentiometric ammonia sensor

V2O5-WO3-TiO2 mixed metal oxide catalyst was synthesized by impregnation method for fabricating sensing electrodes of potentiometric ammonia sensor in this paper. The sensing electrodes were sintered from 650 °C to 900 °C to obtain different electrode microstructures. Crystalline structures of the sensing materials were analyzed by X-ray powder diffraction, and the sensing electrode microstructures were characterized by environmental scanning electron microscopy. Sintering temperature strongly affects the microstructure and the sensitivity of the sensing electrode. With the increment of sintering temperature, the slope of semi-logarithmic characteristic curves increased but began to fall when temperature was more than 750 °C. The effect of sintering temperature on the response and recovery property has similarities, the sensors sintered at 750 °C and 700 °C show the shortest response/recovery times. The increase of the sintering temperature is beneficial for a stronger bond between sensing electrode and YSZ electrolyte, and this could increase the amount of three-phase boundary, and improve the sensor performance. High temperature promotes the V2O5 volatilization, anatase TiO2 grains growing up and the anatase to rutile phase transition, further cause the reduction of the electrode specific surface area. The volatilization of V2O5 and the destruction of high dispersion V2O5 resulted from the growing up of the carrier TiO2, are responsible for the degraded properties of sensing electrode. The suitable operating temperature for this type NH3 sensor is 550 °C based on the compromise of various factors which could influence the sensor performance.