An impedimetric NH3 sensor based on YSZ and spinel-type oxide with θ response

Abstract

Impedimetric NH3 sensors using Yttria-stabilized zirconia (YSZ) as solid electrolyte and spinel-type oxide as sensing electrode (SE) were fabricated. Phase angle (θ) was employed as response signals to evaluate their sensing performance, as a comparison, modulus value (|Z|) response was also examined. The SE materials with nanostructure were in-situ introduced into the YSZ porous skeleton by impregnation technique. A series of spinel-type oxide MFe2O4 (M = Ni, Zn and Co) were examined, and among these oxides, NiFe2O4 was found to be the most excellent SE for NH3 sensor. Sensing performance of the sensor was optimized by adjusting the loading amount and calcination temperature of the sensing material NiFe2O4 and the sensor exhibits the best performance when the loading amount is 0.585 mg and the calcination temperature is 800 °C. Sensing performance of the sensor was tested in 50−1000 ppm NH3 with temperature varying from 400 to 650 °C. Compared with modulus value (|Z|), θ as response signal improves sensing performance of NH3 sensor. The sensor exhibits short recovery time, high sensitivity and reproducible response at 600 °C. The sensor has good anti-interference capability to CO2, CH4, H2, NO2 and NO, but O2 and relative humidity (RH) have a certain effect on sensing performance.