Figaro Engineering Inc.

Mazda Motor Corporation

Katsuyuki Tanaka

Kousuke Ihokura

Nobuaki Murakami

Kazunari Komatsu

Kazuo Onaga

An exhaust gas sensor in which a metal oxide semiconductor containing at least one member of a group of elements consisting of Sn, Fe, Ni and Co and Pt electrodes having ZrO.sub.2, deposited in the grain boundary are used. Such metal oxide semiconductors include, for example, SnO.sub.2, BaSnO.sub.2, BaSnO.sub.3, SrSnO.sub.3, and CaSnO.sub.3. The exhaust gas sensors are manufactured by mixing such compounds as BaCO.sub.3, SrCO.sub.3 or CaCO.sub.3 with SnO.sub.2 in equimolar ratio to react them in air at 1200.degree. C. for four hours. The compounds thus obtained were pulverized and Pt electrodes with ZrO.sub.2 were imbedded therein, then were molded into sensor chips. The chips thus molded were baked by heating in air. After the chip has been sintered the exhaust gas sensor was assembled. It comprised an insulating substrate of alumina, etc. having a recess provided at one end thereof in which the aforementioned sensor chip was housed. The electrodes on the chip were housed in grooves provided in the substrate with their ends connected with base metal outside leads. Then an alumina sheet was pasted on the substrate, leaving a gap along the circumferential rim of the chip, thereby shielding and protecting the electrode from the atmosphere.

Exhaust gas sensor

A combustion gas sensor and material therefore responsive to changes in the composition of ambient atmospheres wherein the sensing element includes SnO.sub.2 crystals having a mean d of approximately 500-3200 .ANG. and having a surface area to mass ratio S of 1-8 m.sup.2 /g a process for making same. Preferably, the standard deviation of crystal size distribution is 0.2d.

Exhaust gas sensor and process for producing same

A combustion gas sensor and material therefore responsive to changes in the composition of ambient atmospheres wherein the sensing element includes SnO.sub.2 crystals having a means d of approximately 500-3200 .ANG. and having a surface area to mass ratio S of 1-8 m.sup.2 /g a process for making same. Preferably, the standard deviation of crystal size distribution is 0.2d.

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Suita, Japan

Katsuyuki Tanaka