Patent ID: 7163609

Claim:
A gas sensor ( 1 a ) having a laminate comprising: an alumina substrate ( 11 ) having a heating resistor ( 115 ) embedded in the alumina substrate ( 11 ); a first oxygen-ion conductive solid electrolyte layer ( 131 ) containing zirconia and alumina and partly constituting an oxygen-detecting cell ( 13 ) and said first solid electrolyte layer ( 131 ) being laminated with said alumina substrate ( 11 ); a second oxygen-ion conductive solid electrolyte layer ( 121 ) containing zirconia and alumina and partly constituting an oxygen-pumping cell ( 12 ); an ion-leakage preventing ceramic spacer ( 143 ) for preventing oxygen-ions from leaking from the second oxygen-ion conductive solid electrolyte layer ( 121 ) to the first oxygen-ion conductive solid electrolyte layer ( 131 ), said spacer ( 143 ) being laminated between said first and second oxygen-ion conductive solid electrolyte layers ( 131 , 121 ); and a gas-diffusion space ( 141 ) formed between an electrode ( 133 ) of the oxygen-detecting cell ( 13 ) and an electrode ( 126 ) of the oxygen-pumping cell ( 12 ); wherein the first and second oxygen-ion conductive solid electrolyte layers contain alumina grains, and wherein the second oxygen-ion conductive solid electrolyte layer ( 121 ) contains alumina in an amount less than that of the first oxygen-ion conductive solid electrolyte layer ( 131 ).