Abstract: Composite ceramic articles formed by integrally assembling a plurality of previously molded constituent members without applying an adhesive to their joints and designed to have a density than higher 98% of the theoretical value, and a flexural strength greater than 50 kg/cm.sup.2 at 1200.degree. C., and a method of producing ceramic articles of particularly complicated shape which comprises the steps of previously molding a plurality of constituent members of complicated shape and later integrally assembling said constituent members without applying an adhesive to their joints.

Abstract: Disclosed is a silicon nitride-based sintered material having high heat resistance and containing crystal compounds prepared from the silicon nitride and at least one oxide of a rare earth element.

Abstract: Ceramics having nonlinear voltage characteristics in which (1) zinc oxide is used as a main component and (2) praseodymium, (3) one or more of magnesium or calcium, and (4) cobalt are added thereto as subcomponents, in elemental form or as a compound thereof, in an amount of from about 0.08 to about 10.0 atomic % for praseodymium, from about 0.08 to about 10.0 atomic % for the one or more of magnesium or calcium, and from about 0.1 to about 8.0 atomic % for the cobalt, each calculated as praseodymium, magnesium or calcium and cobalt.

Abstract: Disclosed is a silicon nitride-based sintered material having high heat resistance and containing crystal compounds prepared from the silicon nitride and at least one of oxides of the elements belonging to the III A group in the periodic table.

Abstract: A method of forming a second semiconductor layer on a first semiconductor layer by vapor growth is disclosed. The two semiconductor layers are of the same conduction type but have different impurity concentrations. In the forming process, a doping gas is supplied before the vapor growth of the second semiconductor layer is started whereby a steep impurity distribution is established in the vapor-growth boundary.