Effects of sintering temperature on the NH3 sensing properties of Mg2Cu0.25Fe1O3.75 electrode for YSZ-based potentiometric NH3 sensor

Mg2Cu0.25Fe1O3.75 mixed metal oxides have been synthesized by a co-precipitation method for fabricating NH3 sensors electrodes. The sensor electrodes were sintered at 1000 °C, 1100 °C, 1200 °C, and 1300 °C to obtain different electrode microstructures. The electrodes were characterized by X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method and Environmental Scanning Electron Microscope (ESEM). NH3 response performances of the NH3 sensors to different concentrations of test gases (20–400 ppm NH3) were evaluated at 400 °C. The influences of sintering temperature on the microstructures, NH3 sensing performances, and electrochemically catalytic activity of Mg2Cu0.25Fe1O3.75 electrodes were investigated. The electrode sintered at 1200 °C exhibited the biggest response (about 110 mV for 400 ppm NH3) and the highest NH3 sensitivity (72 mV/decade NH3) of all the electrodes. Moreover, the response time and recovery time were within 8–4 s and 8–14 s, respectively. The enhanced NH3 sensing performances of the Mg2Cu0.25Fe1O3.75 electrodes may be attributed to electrodes׳ larger electrochemically catalytic activity and more quantity of triple-phase boundary (TPB) of the sintered three-dimensional network electrode structure.