A Novel Highly Sensitive NO2 Sensor Based on Perovskite Na0.5+xBi0.5TiO3−δ Electrolyte

AbstractNOx is one of dangerous air pollutants, and the demands for reliable sensors to detect NOx are extremely urgent recently. Conventional fluorite-phase YSZ used for NOx sensor requires higher operating temperature to obtain desirable oxygen ion conductivity. In this work, perovskite-phase Na0.5Bi0.5TiO3 (NBT) oxygen conductor was chosen as the solid electrolyte to fabricate a novel highly sensitive NO2 sensor with CuO as the sensing electrode and Pt as reference electrode. Na dopped Na0.5Bi0.5TiO3 greatly improved the sensing performance of this sensor. The optimal sensor based on Na0.51Bi0.50TiO3−δ exhibited good response-recovery characteristics to NO2 and the response current values were almost linear to NO2 concentrations in the range of 50–500 ppm at 400–600 °C. The response current value towards NO2 reached maximum 11.23 μA at 575 °C and the value on NO2 is much higher than other gases (CH4, C2H4, C3H6, C3H8, CO), indicating good selectivity for detecting NO2. The response signals of the sensor were slightly affected by coexistent O2 varying from 2 to 21 vol% at 575 °C. The response current value decreased only 4.9% over 2 months, exhibiting the potential application in motor vehicles.