Patent ID: 8613844

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; wherein the laminate is a co-fired laminate; wherein the first and second oxygen-ion conductive solid electrolyte layers ( 131 , 121 ) contain 10-80% by weight of alumina, respectively, and an average grain size of alumina contained in the first and/or second oxygen-ion conductive solid electrolyte layers ( 131 , 121 ) is less than 1 micrometer; and further comprising a gas-diffusion passage ( 142 ) through which the measurement gas enters the gas diffusion space ( 141 ), said gas-diffusion passage ( 142 ) being formed through the ion-transfer prevention spacer ( 143 ), wherein the area of the electrode ( 133 ) of the oxygen-detecting cell ( 13 ) is 15 to 80% of that of electrode ( 126 ) of the oxygen-pumping cell ( 12 ), wherein the area of the electrode ( 126 ) of the oxygen pumping cell ( 12 ) is in a range of 6-10 mm 2 , and wherein a distance between the electrode ( 133 ) of the oxygen-detecting cell ( 13 ) and the electrode ( 126 ) of the oxygen-pumping cell ( 12 ) is 20 to 80 micrometers.