Reducing gas sensor

摘要

This invention provides a reducing gas sensor which has a gas sensitive element composed of, as a main constituent, gamma -ferric oxide ( gamma -Fe2O3) and, as an additive, at least one compound in the group of WO3, MoO3, SiO2, GeO2, Li2O, Na2O, K2O, CaO, SrO, BaO, Eu2O3, La2O3, CeO2, Al2O3, Ga2O3, In2O3, SnO2, TiO2, MgO, NiO, ZnO, Mn2O3 and Cr2O3, a pair of electrodes and a heater element. The gamma -ferric oxide is in the form of a thin film, a plate or a thin surface layer on a sintered plate of gamma -ferric oxide. The gas sensor of the invention is much improved in the stability during use and also it has a high sensitivity.