Patent ID: 7713393
Filing Date: 2010-05-11
Classification: G01N

Abstract:
1. A gas sensor comprising a gas sensor element which includes: a reference electrode for contacting a reference gas; a solid electrolyte layer having oxygen ion conductivity; a detection electrode for contacting a gas to be measured; and an electrode-protecting layer covering said detection electrode, the electrode-protecting layer comprising a porous body carrying catalytic metal, wherein said electrode-protecting layer includes: a detection electrode side portion having a catalytic metal loading ratio of more than 0% by weight and not more than 0.005% by weight; and a surface side portion provided closer to the outer surface of said electrode-protecting layer than said detection electrode side portion, said surface side portion having a catalytic metal loading ratio of 0.01% by weight or more, wherein the catalytic metal loading ratio of said electrode-protecting layer decreases in a thickness direction from said outer surface side of said electrode-protecting layer to the detection electrode side of said electrode-protecting layer, wherein said electrode-protecting layer has a thickness of from 150 to 500 μm, wherein the detection electrode side portion is a portion of the electrode-protecting layer which has a 25 μm thickness from the detection electrode, and the surface side portion is a portion of the electrode-protecting layer which has a 25 μm thickness from the outer surface, and wherein the catalytic metal loading ratios of the electrode-protecting layer have consecutive 25 μm thickness ranges that progressively decrease from the outer surface side to the detection electrode side in the thickness direction.