Abstract: To increase the sensitivity of internal combustion engine exhaust gas sensors, which provide a voltage jump output upon transition of the composition of the exhaust between reducing and oxidizing state, and to maintain the porosity of a platinum, or platinum metal alloy layer forming an electrode on a body of zirconium dioxide, the electrode or electrode layer has dispersed therein an oxide or a carbide of a metal which impedes or inhibits recrystallization at the temperatures to which the sensor is exposed, for example 1000.degree. C.

Abstract: To improve adhesion of a porous cover layer over a platinum or platinum-rhodium electrode layer on a solid electrolyte body, for example of stabilized zirconium dioxide, the electrode layer is applied in form of interrupted, adjacent strips leaving gaps exposing the solid electrolyte body therebeneath. The porous cover layer will adhere well to the solid electrolyte body, thus protecting both the electrode and the cover layer against flaking off under high-temperature and temperature variation conditions. The sensitivity can be improved by interposing a layer of ceramic mixed with platinum or a platinum rhodium between the solid electrolyte body and at least some of the electrode strips, the adhesion of the porous cover layer over the interposed thick-film layer, where exposed between the portions of the electrode on the solid electrolyte body being sufficient for the intended purpose.

Abstract: Electro-chemical sensor to determine oxygen concentration in hot internal combustion exhaust gases in the form of a closed, tubular element having a solid ion conductive electrolyte; an electron-conductive coating on the inner surface thereof; a porous or fissured electron conductive layer on the outer surface of said solid electrolyte or on a part of said surface, part of the pores or fissures being macroporous, said layer being of a material which catalyzes the formation from said hot exhaust gases of those compounds that are thermodynamically stable at the exhaust temperature; and a porous protective electrically insulating coating on said porous electron-conductive layer. Preferably, a top coating of a heat-resistant metal is applied, which top coating has additionally properties to act as a getter with respect to poisons affecting the catalyzing material.

Abstract: Methods for making an exhaust-gas-sensing element which is an oxygen concentration cell having a solid electrolyte with an electron-conductive surface on the side exposed to the reference air and a catalytic electron-conductive layer containing micro pores which extend through to the solid electrolyte on the other surface which is adapted to be exposed to the exhaust gases. The electron-conductive catalytic layer is covered with a porous protective layer. The method comprising applying the catalytic layer by means of thin layer techniques and then heating to form the micro pores; or by applying a paste comprising ceramic particles, catalytic particles and a thinning oil and sintering.