Abstract: A spinel single crystal substrate for epitaxial growth thereon of a semiconductor layer to manufacture semiconductor devices. Magnesium titanate is substituted for at least a portion of magnesium aluminate of which the spinel essentially consist in general. A preferred mol ratio of the magnesium titanate to the magnesium aluminate is between 5:95 and 40:60 when a silicon layer is to be epitaxially grown on the substrate as the semiconductor layer.

Abstract: Dense mullite ceramic bodies are manufactured from a mullite-proportioned mixture of alumina (Al.sub.2 O.sub.3) and silica (SiO.sub.2) containing a critically small amount of titania (TiO.sub.2). The preferred concentration of titania based on the mullite (Al.sub.6 Si.sub.2 O.sub.13) is from 0.5 to 1.0% by weight, which by means of a specific sequence of processing steps results in mullite bodies having densities of 2.5 g./cc. or greater. More specifically, a molecularly intermixed mixture is calcined at a temperature of 900 to 1150.degree. C. to convert the mixture to mullite in intimate association with the small percentage of titania, which is present essentially as fine titania crystals. The calcined mullite is ground to break up the aggregates and obtain a mixture of essentially discrete crystals of mullite and titania. The ground mixture is formed into the shape of the desired bodies, and the bodies are heated at an effective sintering temperature to produce the dense mullite bodies.

Abstract: In a method of forming a sintered, ceramic product, aluminium nitride is reacted with silica at a temperature of between 1200.degree. and 2000.degree. C to form a single phase silicon aluminium oxynitride ceramic material, the reaction mixture at said temperature containing not more than 60% by weight of the aluminium nitride and also containing first and second metal oxides other than silica. The metal oxides are arranged so that they do not introduce into the mixture a combination of magnesium oxide and alumina alone and further are arranged so that during the reaction they combine with part of said silica to form a silicate glass having a liquidus temperature below that of the silicate glass which would be formed from silica with either of said metal oxides alone. The silicate glass formed then aids densification of the ceramic material during sintering.

Abstract: This invention relates to ceramic compositions of tungsten and tantalum oxides including 0 to 33 1/3 mole percent of a metal oxide such as hafnia. These ceramics are characterized by melting points greater than about 1400.degree.C and selectively controlled coefficients of thermal expansion of essentially zero to a negative value in the temperature range of 20.degree. to 1000.degree.C.

Abstract: Fine crystalline powder, from 0.02 to 0.2 micron in average particle size, of a composition Pb(Zr.Ti)O.sub.3. Parts of Zr and Ti of the composition may be substituted for with Mn and Sb, Nb, and/or Ta. The powder is produced by preparing an acidic aqueous solution of the constituent metallic ions, neutralizing the solution to provide a suspension of hydroxides of the metals, and subjecting the suspension to hydrothermal reaction at 150.degree.-300.degree.C. The powder provides piezoelectric ceramics of a high sintered density without resorting to hot pressing.

Abstract: Oxide compositions containing niobium pentoxide and an oxide selected from the group consisting of hafnia, titania, and zirconia have electrical conductivity characteristics which vary greatly depending on the oxygen content.

Abstract: An intergranular insulation type semiconductive ceramic composition comprising a major proportion of strontium titanate (SrTiO.sub.3), a minor amount of niobium oxide (Nb.sub.2 O.sub.5) or tantalum oxide (Ta.sub.2 O.sub.5), a minor amount of either germanium oxide (GeO.sub.2) or zinc oxide (ZnO) and having diffused therein either bismuth oxide (Bi.sub.2 O.sub.3) or a mixture of bismuth oxide, lead oxide (PbO) and boric oxide (B.sub.2 O.sub.3). The material is especially useful as a capacitor.

Abstract: A process for preparation of a positive temperature coefficient material of the barium titanate/barium zirconate type. An aqueous feed mixture comprising a compound of barium or other suitable divalent cation and an organic compound of titanium or zirconium is introduced into an anterior zone adjacent a heated reaction zone in a rotating, inclined, tubular furnace or other useful calcining equipment. At the entrance of the reaction zone, the feed mixture forms a mass which swells in response to heat emanating from the tube wall and the reaction zone, undergoes dehydration and ignites. Particles break away from the mass and enter the reaction zone where they are calcined in an oxidizing atmosphere to produce the product material. Both these particles and the product material are milled as they pass through the reaction zone. Product material discharging from the reaction zone is collected for use in the manufacture of positive temperature coefficient elements.

Abstract: A gas sensor, and its method of manufacture, particularly useful as an exhaust gas sensor for an internal combustion engine air/fuel ratio system, is disclosed. The sensor is comprised of a sintered ceramic body of transition metal oxide, such as titania, and includes a pair of spacedapart electrodes. As the partial pressure of oxygen in the gas being sensed varies in response to variations in the inlet air/fuel mixture ratio, the resistance of the ceramic material varies. The active portion of the sensor body is a substantially uniform body of porous ceramic material having a density of less than about 85% of theoretical density and a modulus of rupture in excess of 11,000 psi. The sensor is fabricated from a very pure transition metal oxide powder having a very fine and highly uniform particle size. The transitional metal oxide is selected so that the operating temperature of the resulting device is less than about 75% and preferably less than about 50% of the melting temperature of the metal oxide.

Abstract: Heat-resistant masking compositions suitable for use in masking vitreous and semicrystalline ceramic surfaces from coating by liquid-sprayed coating compositions to provide permeation-resistant masks which are readily removable even after high temperature firing are described. The masking compositions comprise bentonite clay and a finely-divided refractory inorganic oxide release agent.