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Mg 2 Cu 0.25 Fe 1 O 3.75 mixed metal oxides have been synthesized by a co-precipitation method for fabricating NH 3 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). NH 3 response performances of the NH 3 sensors to different concentrations of test gases (20–400 ppm NH 3 ) were evaluated at 400 °C. The influences of sintering temperature on the microstructures, NH 3 sensing performances, and electrochemically catalytic activity of Mg 2 Cu 0.25 Fe 1 O 3.75 electrodes were investigated. The electrode sintered at 1200 °C exhibited the biggest response (about 110 mV for 400 ppm NH 3 ) and the highest NH 3 sensitivity (72 mV/decade NH 3 ) of all the electrodes. Moreover, the response time and recovery time were within 8–4 s and 8–14 s, respectively. The enhanced NH 3 sensing performances of the Mg 2 Cu 0.25 Fe 1 O 3.75 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. [ABSTRACT FROM AUTHOR]

In this work, a (La0.8Sr0.2)2FeNiO6−δ (LSFN) powder semiconductor oxide with a double-perovskite structure was synthesized by a polymeric precursor method to fabricate a sensitive electrode (SE) for a NO x sensors based on yttria-stabilized zirconia (YSZ). The LSFN powder and the LSFN-SEs sintered at different temperatures (1000, 1100 and 1200°C) were characterized by X-ray diffraction (XRD). The morphologies of LSFN-SEs were observed by environmental scanning electron microscopy (ESEM). The sensors with LSFN-SEs were tested over a temperature range of 550–800°C. Electrochemical impedance spectroscopy (EIS) was also performed to investigate the electrochemical processes that are affected by the NO2 concentration. The results demonstrated that the double-perovskite type electrode material possessed good thermal stability. The NO2 sensitivity of the sensor was found to be modulated by the morphology of LSFN–SE. The sensor showed a higher sensitivity and a better selectivity to NO2 than that to NO. The impedance changed when the NO2 concentration was varied, which was attributed to the interaction of the NO2 with the SE. [ABSTRACT FROM AUTHOR]