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1. (WO2001031324) OXYGEN SENSOR AND METHOD FOR MANUFACTURING SENSOR ELEMENT

Pub. No.:    WO/2001/031324    International Application No.:    PCT/JP2000/007606
Publication Date: Fri May 04 01:59:59 CEST 2001 International Filing Date: Sat Oct 28 01:59:59 CEST 2000
IPC: G01N 27/407
Applicants: NGK SPARK PLUG CO., LTD.

ISOMURA, Hiroshi

ATSUMI, Takayoshi

SHIONO, Koji

TAKAGI, Masamine

Inventors: ISOMURA, Hiroshi

ATSUMI, Takayoshi

SHIONO, Koji

TAKAGI, Masamine

Title: OXYGEN SENSOR AND METHOD FOR MANUFACTURING SENSOR ELEMENT
Abstract:
An oxygen sensor equipped with a sensor element having a detection electrode, an electrode-protecting layer and a poisoning prevention layer, characterized in that the poisoning protection layer comprises a composite powder comprising rough particles and fine particles covering the surroundings of said rough particles and holes are present in the composite powder, being not filled with fine particles. Such rough particles and fine particles are preferably ceramic particles, and more preferably, particles of a composite oxide comprising alumina such as spinel which has a peak of size at 10 νm or more and titania particles having a peak of size at 1 νm or less. The poisoning protection layer can be formed by a method comprising applying a slurry containing ceramic powders which are different from each other in specific surface area and particle size, an organic binder and a solvent such as methanol onto the surface of the electrode-protecting layer and then drying. The oxygen sensor is effectively prevented from the poisoning of its detection electrode by lead or the like even in an exhaust gas of a low temperature, and thus, can maintain stable response for a long period of time, that is, is excellent in durability.