Matsushita Electric Industrial Co., Ltd.

Masatake Ayusawa

Seiichi Nakatani

Hideyuki Okinaka

Atsushi Iga

Toshiaki Yagami

Masatugu Yamaguchi

This invention provides a reducing gas sensor which has a gas sensitive element composed of, as a main constituent, .gamma.-ferric oxide (.gamma.-Fe.sub.2 O.sub.3) and, as an additive, at least one compound in the group of WO.sub.3, MoO.sub.3, SiO.sub.2, GeO.sub.2, Li.sub.2 O, Na.sub.2 O, K.sub.2 O, CaO, SrO, BaO, Eu.sub.2 O.sub.3, La.sub.2 O.sub.3, CeO.sub.2, Al.sub.2 O.sub.3, Ga.sub.2 O.sub.3, In.sub.2 O.sub.3, SnO.sub.2, TiO.sub.2, MgO, NiO, ZnO, Mn.sub.2 O.sub.3 and Cr.sub.2 O.sub.3, 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.

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Hirakata, Japan

Masatake Ayusawa