A Novel Highly Sensitive NO ₂ Sensor Based on Perovskite Na _0.5+xBi _0.5TiO _3−δ Electrolyte

Abstract

NO _x is one of dangerous air pollutants, and the demands for reliable sensors to detect NO _x are extremely urgent recently. Conventional fluorite-phase YSZ used for NO _x sensor requires higher operating temperature to obtain desirable oxygen ion conductivity. In this work, perovskite-phase Na _0.5Bi _0.5TiO ₃ (NBT) oxygen conductor was chosen as the solid electrolyte to fabricate a novel highly sensitive NO ₂ sensor with CuO as the sensing electrode and Pt as reference electrode. Na dopped Na _0.5Bi _0.5TiO ₃ greatly improved the sensing performance of this sensor. The optimal sensor based on Na _0.51Bi _0.50TiO _3−δ exhibited good response-recovery characteristics to NO ₂ and the response current values were almost linear to NO ₂ concentrations in the range of 50–500 ppm at 400–600 °C. The response current value towards NO ₂ reached maximum 11.23 μA at 575 °C and the value on NO ₂ is much higher than other gases (CH ₄, C ₂H ₄, C ₃H ₆, C ₃H ₈, CO), indicating good selectivity for detecting NO ₂. The response signals of the sensor were slightly affected by coexistent O ₂ 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.