Abstract: An oxygen gas sensor having a solid electrolyte oxygen gas sensor element, with an inner conductive catalyst electrode on the interior surface and an outer conductive catalyst electrode on the exterior surface thereof, which has a high voltage output and lower internal resistance is produced by chemically activating said inner conductive catalyst electrode with an inorganic acid or an acid salt. By also subjecting said outer conductive catalyst electrode to a direct current activation under a reducing atmosphere, even more improved properties, such as fast switching response, are achieved.

Abstract: A solid electrolyte sensor for sensing oxygen in exhaust gases having a solid electrolyte body of a thimble-like design with an inner conductor thereon and a nonreactive but compatible bonding layer of magnesium or calcium oxide over the outer surface of the electrolyte body and a conductive catalyst layer superimposed on the bonding layer.

Abstract: A solid electrolyte oxygen sensor has a protective coating to protect a catalyst or conductive film thereon, which coating is formed as an inorganic reaction product of an oxide material and an inorganic acid which forms a matrix to bond the oxide material as an adherent coating over the film.