Patent ID: 7704358

Claim:
An oxygen sensor comprising: a base body portion; and a plurality of function layers laminated on a surface of the base body portion, the function layers including a solid electrolyte layer adapted to conduct oxygen ions, a reference electrode layer located on a base body portion side of the solid electrolyte layer, a sensing electrode layer located on the opposite side of the solid electrolyte layer to the reference electrode layer, a heater portion adapted to activate the solid electrolyte layer by heating, and a gas diffusion layer formed between the reference electrode layer and the base body portion, and adapted to diffuse a reference gas within the gas diffusion layer, the gas diffusion layer being formed to have a porosity indicating a limit current value ranging between 60 μA and 200 μA, the limit current value being a value of a current flowing between the reference electrode layer and the sensing electrode layer when the current flowing therebetween becomes substantially constant during the process of bringing higher a voltage applied between the reference electrode layer and the sensing electrode layer.