Sensing properties of YSZ-based NOx sensors with double-perovskite (La0.8Sr0.2)2FeNiO6−δ-sensing electrodes

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 NOx 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.