Abstract: An oxygen sensor for detecting an oxygen concentration in a gas under test such as exhaust gas from an internal combustion engine of an automobile. The oxygen sensor comprises an oxygen concentration sensing element made of an oxygen ion conductive metal oxide which produces an electromotive force in accordance with a difference between an oxygen concentration in the gas under test and an oxygen concentration in a reference gas, a porous layer of refractory metal oxide formed on a surface of the oxygen concentration sensing element which is to be exposed to the gas under test, and an electrode formed thereon. The peel-off of the electrode is prevented and a high-response oxygen sensor is provided.

Abstract: A gas composition detector, particularly an oxygen concentration detector includes a metal oxide an electrical resistance or an electromotive force of which is changed by oxygen ions which are conducted in accordance with a difference between an oxygen concentration of gas being examined and an oxygen concentration of a reference gas. A surface of the metal oxide is coated with a conductive metal electrode, and a metal which is the same as or different than the conductive metal penetrates into the metal oxide at the interface of the metal oxide and the conductive metal, whereby the tear-off of the electrode is prevented.

Abstract: A sintered body of zirconia material for an oxygen concentration sensor exhibiting an electromotive force in accordance with the difference in the concentration of oxygen between a gas tested and a reference gas, consisting essentially of partially stabilized sintered zirconia and at least one additive selected from the group of yttrium oxide, calcium oxide and ytterbium oxide which zirconia has a cubic phase and a monoclinic phase existing in mingling relation. The ratio of the X-ray diffraction intensity of the surface (111) of the monoclinic phase to the X-ray diffraction intensity of the surface (111) of the cubic phase or the ratio I(111)/I(111) is in the range between 0.05 and 0.40, and the value of the X-ray diffraction intensity ratio caused by heating the sintered zirconia material to, and holding the same at, the temperature range between 200.degree. and 300.degree. C. minus the former ratio of the X-ray diffraction intensity is in the range between -0.05 and +0.10.

Abstract: An oxygen concentration detector comprises an oxygen concentration sensor made of an oxygen ion conductive metal oxide which produces an electromotive force in accordance with a difference between an oxygen concentration in gas components of a gas under test and an oxygen concentration in a reference gas, an electrode formed on a surface of the oxygen concentration sensor which is to be exposed to the gas under test and an electrode formed on a surface of the oxygen concentration sensor which is to be exposed to the reference gas so that the electromotive force produced by the oxygen concentration sensor is taken across the electrodes, a first porous coating of a refractory metal oxide formed on the surface of the electrode which is to be exposed to the gas under test, said first coating having a number of pores through which the gas under test can pass, and a second porous coating of a refractory metal oxide formed on the surface of the first coating, said second coating having a number of pores which are la

Abstract: An oxygen sensor for detecting an oxygen concentration in exhaust gas such as that exhausted from an internal combustion engine, said sensor comprising a solid electrolyte made of an oxygen ion conducting metal oxide which is subjected to gas to be monitored and reference gas, e.g., atmosphere and generating an e.m.f. which corresponds to a difference between oxygen concentrations of both gases. Said solid electrolyte has conductive ribs acting as an auxiliary electrode strongly bonded to that surface thereof which is subjected to the exhaust gas.

Abstract: an oxygen concentration detector of a waterproof construction comprises an oxygen ion conduction metal oxide (1) which produces an electromotive force in accordance with a difference between an oxygen concentration in gas component in a gas under test such as exhaust gas from an internal combustion engine of an automobile and an oxygen concentration in the atmosphere. The structure includes a coaxially arranged inner tube and an outer tube with the inner tube being housed in the outer tube with a water proof structure being interposed therebetween. The inner tube constitutes a lead wire to be electrically connected to that one of two electrodes for taking out the electromotive force which is created. The outer tube (18) serves to expose the inner electrode (2) to the atmosphere at a site such that water may not be splashed into the interior of the sensor.

Abstract: an improved oxygen concentration detector is described having an oxygen concentration sensor which produces an electromotive force in accordance with a difference between an oxygen concentration in the gas components of a gas under test and an oxygen concentration in a reference gas, and first and second electrodes formed on the gas-under-test side and the reference gas side, respectively, of the oxygen concentration sensor, so that the electromotive force produced by the oxygen concentration sensor is taken across the two electrodes, in which the improvement comprises a first protective member arranged to cover the first electrode on the oxygen concentration sensor and having a number of pores through which the gas under test can pass, and a second protective member arranged between the first electrode and the first protective member also having a number of pores through which the gas under test can pass.