Abstract: Zirconia and/or hafnia-containing ceramics having high electric resistivity and mechanical strength which consists essentially of 5-30 mol % of at least one component of Group A consisting of YO.sub.1.5, ScO.sub.1.5, SmO.sub.1.5, EuO.sub.1.5, GdO.sub.1.5, TbO.sub.1.5, DyO.sub.1.5, HoO.sub.1.5, ErO.sub.1.5, TmO.sub.1.5, YbO.sub.1.5, LuO.sub.1.5, CaO and MgO, 5-40 mol % of at least one component of Group B consisting of NbO.sub.2.5 and TaO.sub.2.5 and 30-90 mol % of at least one component of Group C consisting of ZrO.sub.2 and HfO.sub.2, said ceramics preferably satisfying the following equation.SIGMA.{(4-(ion valence number of each component of Group A)).times.(number of mole of each component of Group A)}.ltoreq.(total number of mole of components of Group B).and crystal phase of said ceramics being preferred to be composed mainly of tetragonal phase.

Abstract: An oxygen concentration regulator for regulating the oxygen concentration in gases comprises an oxygen ion conductive solid electrolyte body, at least two separate electrodes contacting the solid electrolyte body so as to form an electrolysis cell, said cell having complex impedance characteristics which when graphed exhibit a curve similar to that shown in FIG. 3 hereof, AC power supplying means for applying an AC electric voltage across said electrolysis cell, said AC power supplying means being operable only at an AC frequency which is not lower than a frequency whose complex impedance characteristics, when graphed in the manner shown in FIG. 3 hereof, correspond to point B of said graphed complex impedance characteristic curve, and means for affirmatively applying a DC current across said electrodes, said DC current regulating the oxygen concentration in gases.

Abstract: The disclosed oxygen concentration detector includes at least one resistive body and at least one semiconductor whose resistance varies with oxygen partial pressure, and an alternating current of a specific frequency is applied to the resistive body so as to raise the temperature thereof, which resistive body is adapted to heat the semiconductor.

Abstract: An oxygen concentration detector comprises an oxygen ion conductive solid electrolyte body and electrodes provided thereon to form an oxygen concentration cell for detecting oxygen partial pressure in a gas such as exhaust gas from an internal combustion engine. The oxygen concentration detector according to the invention further comprises an AC power source supplying to the electrodes an AC current having a frequency at which a polarization of alternating current component is caused mainly due to a polarization of the solid electrolyte body to heat it, and a DC power source supplying a direct current to the electrodes so as to control oxygen concentration on the side of at least one electrode of the oxygen concentration cell to detect its electromotive force.

Abstract: An oxygen concentration detector comprises an oxygen ion conductive solid electrolyte and electrodes provided thereon to form an oxygen concentration cell for detecting oxygen partial pressure in a gas such as exhaust gas from an internal combustion engine. The oxygen concentration detector according to the invention further comprises an AC power source supplying to the electrodes an AC having a frequency at which a polarization of AC component is caused mainly due to a polarization of the solid electrolyte to detect an impedance of the solid electrolyte and the electromotive force of the oxygen concentration cell.

Abstract: The disclosed oxygen concentration detector includes at least one oxygen concentration cell and at least one oxygen-ion-conducting solid electrolyte, and an alternating current of a specific frequency is applied to the oxygen concentration cell so as to raise the temperature thereof, while a direct current is applied to the oxygen-ion-conducting solid electrolyte so as to control the oxygen partial pressure at one or two electrodes of the oxygen concentration cell.

Abstract: The disclosed oxygen concentration detector includes a plurality of resistive bodies at least one of which forms an oxygen concentration cell, and an alternating current of a specific frequency is applied to a selected resistive body so as to raise the temperature thereof, said selected resistive body being adapted to heat the oxygen concentration cell.

Abstract: In a detector to measure the oxygen concentration of a gaseous mixture such as automobile exhaust gas by using the principle of an oxygen concentration cell made of an oxygen ion conductive solid electrolyte body with electrodes mounted on opposite surfaces thereof, the inventive detector and the method use AC voltage electrode means provided on the solid electrolyte body to apply an AC voltage thereof for heating the detector.

Abstract: ZrO.sub.2 -Y.sub.2 O.sub.3 solid electrolytes having a high strength and an excellent deterioration property so as to be durable for a long time, comprised mainly of cubic crystal and monoclinic crystal or cubic crystal, monoclinic crystal and tetragonal crystal, wherein an average grain size of monoclinic crystal or tetragonal crystal is not greater than 2 .mu.m and a ratio of the intensity of the monoclinic (III) X-ray diffraction line to that of the cubic (200) line is 0.01-2.5. In the case of solid electrolytes comprised mainly of cubic crystal, monoclinic crystal and tetragonal crystal, the following definition is necessary. A ratio of the intensity of the tetragonal (200) X-ray diffraction line to that of the cubic (200) line is not greater than 1.0.

Abstract: A method of removing nitrogen oxides from waste gas exhausted from a heat power plant and any other various kinds of workshops, etc. is disclosed. The method comprises bringing the waste gas into contact with a honeycomb-shaped catalyst under the following three conditions, i.e.(1) a hydraulic diameter of each of the channels extending through the honeycomb-shaped catalyst is larger than 2.0 mm, preferably 2.0 mm to 30 mm,(2) an open frontal area is larger than 50%, preferably 50% to 80%, and(3) a waste gas speed is higher than 0.5 m/sec, preferably 0.5 m/sec to 60 m/sec.

Abstract: Cordierite ceramic honeycomb consisting mainly of cordierite in crystal phase and containing not more than 20% by weight of at least one crystal selected from the group consisting of spinel, mullite and corundum and having a thermal expansion coefficient at a temperature range of 25.degree.-1,000.degree. C. being less than 22.times.10.sup.-7 (1/.degree.C.).

Abstract: Cordierite ceramic consisting mainly of cordierite in crystal phase after fired and having a mean pore size of 2-50 microns and a thermal expansion coefficient of not more than 16.times.10.sup.-7 (1/.degree. C.) over the range of 25-1000.degree. C. and being produced by starting from a batch including a magnesia raw material with an average particle size of 5-150 microns.

Abstract: A ceramic honeycomb composite structure adapted to be used as a catalyst support comprises a ceramic honeycomb body and ceramic layers integrally provided thereon having surfaces including therein microscopic holes, a sum of volumes of the holes 5 microns or more being at least 0.1 cm.sup.3 /g to ensure a sufficient catalyst-supporting property and achieve a high mechanical strength of the structure. On the layers of the structure are provided active material layers onto which a catalytic component is applied to enable it to be used as a catalyst. A ceramic material is extruded through a die to form the ceramic honeycomb body to which is applied ceramic grains and then the body with the grains is dried and sintered to complete the composite structure.

Abstract: An oxygen partial pressure measuring device for determining oxygen partial pressures in exhaust gases emitted from internal combustion engines comprises a metallic vessel mounted within an exhaust pipe of the engine and having an exhaust gas inlet facing to the exhaust gas flow and an exhaust gas outlet formed in a side surface of the vessel, an oxygen concentration cell shutting the exhaust gas out of the air in an air-tight manner, and a monolithic structure, what is called a honeycomb structure, located between the exhaust gas inlet and the oxygen concentration cell within the vessel for burning the exhaust gas.

Abstract: A catalyst support characterized by having a total pore volume ranging 0.05-0.5 cc/g. an average pore diameter ranging from 0.05-5.mu. and consisting mainly of .alpha.-alumina; and an internal combustion engine exhaust gas purifying catalyst made of said catalyst support carrying a catalytic agent.

Abstract: A porous catalyst carrier refractory material with its pores containing internally deposited active alumina, its total pore volume being 0.05-0.50 cc/g, its average pore diameter 0.05-5.0.mu. and its specific surface area 3-60 m.sup.2 /g and a method of making it.