An oxygen sensor for an automobile exhaust system was integrated by planar technology. Powders of perovskite SrTi1-xFexO3-δ were synthesized by a sol-gel method. Micro-powders to compare the properties of powders were also prepared by a solid state reaction after mixing of commercial reagents of SrCO3, TiO2, and Fe2O3. A paste based on nano- and micro-powders was prepared to make a planar device on an Al2O3 substrate by silk screen printing technology. The phase formation and microstructure were analyzed by XRD and SEM, respectively. O2 sensing and electrical properties were measured as a function of thermal treatment conditions, atmosphere, time and temperature. The precursor was transformed into SrTi1-xFexO3-δ at 800~1100 οC in ambient atmosphere. Zero TCR(temperature coefficient of resistance) for perovskite SrTi1-xFexO3-δ powders was measured over 600 οC. There were no interference effect to CH4, CO, NO2 and CO2, but an excellent response and recovery characteristics with oxygen concentration.

Keywords: SrTi1-xFexO3-δ, Perovskite structure, Sol-gel precipitation, Oxygen sensor