Claims for Patent: 5,006,828

Summary for Patent: 5,006,828

Title:	Exhaust gas sensor and process for producing same
Abstract:	A BaSnO.sub.3 exhaust gas sensor and a process for producing the same. Surface reformation of sensor electrodes is done for preventing the deterioration of the sensor response and the corrosion of the electrodes by the Sn in the BaSnO.sub.3. After depositing an oxide film such as La.sub.2 Ti.sub.2 O.sub.7 or MgO on the surface of the electrodes, the electrodes are embedded in BaSnO.sub.3, and the BaSnO.sub.3 is sintered. Through the sintering process, the film of La.sub.2 Ti.sub.2 O.sub.7 or MgO is converted to a conductive complex oxide film by reacting with BaSnO.sub.3. The resultant film contains Ba and Sn elements. CaSnO.sub.3 and SrSnO.sub.3, which are homologous compounds of BaSnO.sub.3, are usable in place of BaSnO.sub.3.
Inventor(s):	Yutaka; Yoshida (Osaka, JP), Kazuo; Onaga (Osaka, JP), Mariko; Hanada (Nara, JP), Kazunari; Komatsu (Hiroshima, JP)
Assignee:	Figaro Engineering, Inc. (Osaka, JP) Mazda Motor Corporation (Osaka, JP)
Application Number:	07/376,044
Patent Claims:	1. An exhaust gas sensor including a perovskite compound ASnO.sub.3 where A represents at least one member selected from the group consisting of Ba, Sr, and Ca, and at least a pair of noble metal electrodes contacted to the ASnO.sub.3, the exhaust gas sensor being characterized in that an electrically conductive complex oxide film of ASnO.sub.3 and a base metal oxide, whose base metal constituent is different from each metal constituent of ASnO.sub.3, is deposited on the surface of the electrodes at the portion thereof in contact with ASnO.sub.3. 2. An exhaust gas sensor as defined in claim 1, wherein the base metal oxide is at least one memeber selected from the group consisting of La oxide, oxide of La and a transition metal element, oxide of Fe and Co, oxide of Fe and an alkaline earth metal element which is different from the alkaline earth metal element of ASnO.sub.3, and oxide of an alkaline earth metal element which is different from the alkaline earth metal element of ASnO.sub.3. 3. An exhaust gas sensor as defined in claim 2, wherein ASnO.sub.3 is BaSnO.sub.3, and the base metal oxide is at least one member selected from the group consisting of an oxide of La and Ti, an oxide of Sr and Fe, and Mg oxide. 4. An exhaust gas sensor as defined in claim 3, wherein the base metal oxide is an oxide of La and Ti.