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

Impedimetric NH 3 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 MFe 2 O 4 (M = Ni, Zn and Co) were examined, and among these oxides, NiFe 2 O 4 was found to be the most excellent SE for NH 3 sensor. Sensing performance of the sensor was optimized by adjusting the loading amount and calcination temperature of the sensing material NiFe 2 O 4 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 NH 3 with temperature varying from 400 to 650 °C. Compared with modulus value (|Z|), θ as response signal improves sensing performance of NH 3 sensor. The sensor exhibits short recovery time, high sensitivity and reproducible response at 600 °C. The sensor has good anti-interference capability to CO 2 , CH 4 , H 2 , NO 2 and NO, but O 2 and relative humidity (RH) have a certain effect on sensing performance.