Abstract: A porous coating, which is effective in restricting the flow of a gas under measurement relatively to the electrode layer of the sensor and protecting the electrode against detrimental influences, is formed by spraying fine particles of a heat-resistant and chemically stable material at a high temperature onto the electrode surface to form a porous layer with pores of a moderate size, then impregnating the porous layer with an aqueous dispersion of fine particles of a similar material followed by baking the impregnated layer, so that the finished coating has pores of appropriate size and total volume.

Abstract: In an oxygen sensor having a solid electrolyte layer such as stabilized zirconia and two electrode layers form respectively on both sides of the electrolyte layer, at least one electrode which is to be exposed to a gas mixture subject to measurement is made of carbon silicide to avoid catalyzing oxidation reactions, optionally with the addition of a minor amount of trisilicon tetranitride as a binder. The sensor features an exact and noticeable dependence of its output voltage on the oxygen concentration in a gas mixture in a non-equilibrated state as typified by an engine exhaust gas.