Abstract: A process for producing a cordierite ceramic product comprises blending a starting cordierite composition which comprises:(a) a clay formulation having a cordierite composition comprising kaolin, talc and aluminium oxide and/or an aluminium compound which is convertible into aluminium oxide;(b) a glass having a cordierite composition;(c) an organic binder; and,(d) water.

Abstract: An oxygen concentration sensor including a solid electrolyte member having two portions, one portion being exposed to a gas of interest and the other portion being exposed to the atmosphere, an inner cover formed with a first space communicating portion arranged to communicate with the other portion of the solid electrolyte member, and a water-proof cover enclosing the inner cover to define a ventilating passage between the inner cover and the water-proof cover and formed with a second space communicating portion maintaining the first space communicating portion of the inner cover in communication with the atmosphere through the ventilating passage. The second space communicating portion of the water-proof cover is axially spaced apart from the first space communicating portion of the inner cover by a predetermined distance. Also included is structure to prohibit the flow of water through said ventilating passage. The second space communicating portion is separated from this structure.

Abstract: A solid electrolyte for an oxygen concentration sensor is provided by mixing ZrO.sub.2 and about 6.5 to 7% by mol of a stabilizer such as Y.sub.2 O.sub.3, grinding the mixture to give a BET specific surface area of about 9 to 20 m.sup.2 /g, adding to the ground mixture a forming aid, forming the mixture into a predetermined configuration and firing the formed mixture at about 1420.degree. to 1480.degree. C. The electrolyte has a surface-average grain size of about 5 microns or less and a structure of a cubic phase and a monoclinic and/or tetragonal phase at the surface thereof and, furthermore, may contain about 5% or less of a monoclinic phase per the total of the cubic and monoclinic phases, in a finely ground state.

Abstract: A solid electrolyte for an oxygen concentration sensor is provided by mixing ZrO.sub.2 and about 7.5 to 8.5% by mol of a stabilizer such as Y.sub.2 O.sub.3, grinding the mixture to have a BET specific surface are of about 9 to 20 m.sup.2 /g, adding to the ground mixture a forming aid, forming the mixture into a predetermined configuration and firing the formed mixture at about 1420.degree. to 1520.degree. C. The electrolyte has a surface-average grain size of about 5 microns or less and a structure of a cubic phase alone at the surface thereof and even in a finely ground state.

Abstract: A solid electrolyte for an oxygen concentration sensor is provided by mixing ZrO.sub.2 and about 6.5 to about 8% by mol of a stabilizer such as Y.sub.2 O.sub.3, grinding the mixture to give a BET specific surface area of about 9 to 20 m.sup.2 /g, adding to the ground mixture a forming aid, forming the mixture into a predetermined configuration and firing the formed mixture at about 1420.degree. to 1570.degree. C. The electrolyte has a surface-average grain size of about 5 microns or less and a structure of a cubic phase alone at the surface thereof and, furthermore, may contain about 5% or less of a monoclinic phase per the total of the cubic and monoclinic phases, in a finely ground state.

Abstract: An oxygen concentration sensing apparatus in which a block of an oxygen-ion conductive solid electrolyte is interposed between a first electrode and a second electrode disposed opposite to each other. The first electrode is made of a catalytic metal and is exposed at a portion thereof on a surface of the solid electrolyte block, and an electrical insulating heat-resistive layer having a plurality of communication pores covers the exposed portion of the first electrode. The second electrode is porous and made of a catalytic metal. The solid electrolyte is wholly exposed to a stream of gases containing oxygen whose concentration is to be measured, and during measurement, a current source supplies continuously an electric current in a direction from the first electrode toward the second electrode.

Abstract: In an oxygen concentration sensing apparatus comprising a solid, oxygen ion conductive, electrolyte and intervening between two electrodes to generate across the two electrodes a potential difference due to a difference in oxygen concentrations at the boundaries between the two electrodes and the solid electrolyte, one of the two electrodes is made of a metal performing catalytic action, one end portion of the one electrode is embedded in the solid electrolyte to be fixed thereby, the other end portion of the one electrode projects outwardly of the solid electrolyte, a portion of the one electrode contacting with an outer surface of the solid electrolyte is hermetically sealed with a nonconductive layer of a heat-resistant material, and the other electrode is made of a porous metal performing catalytic action and is disposed on the outer surface of the solid electrolyte but preventing the other electrode from being in contact with the one electrode.

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 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.