Abstract: An excellent oxide series superconductive sintered body can be provided which can be joined to a metallic member easily and economically at low temperatures without causing peeling-off and deformation of the metallic member, cracks in the sintered body, and deterioration of the sintered body, by coating the surface of the sintered body with a coating metal. A method of producing the sintered body having the coating metal is also provided.

Abstract: A sintered body of a ceramics material consisting essentially of a mixture of lanthanum chromite of the formula of LaCrO.sub.3 with an oxide of a specifically limited metal, or consisting essentially of lanthanum chromite, whose Cr is partly replaced by a specifically limited metal, has high mechanical strength and electroconductivity and is very useful as an interconnecting member of fuel cell. A mixture of lanthanum chromite, whose Cr is partly replaced by a specifically limited metal, with an oxide of a specifically limited metal is effective for obtaining a sintered body having high mechanical strength and electroconductivity in a high sinterability.

Abstract: Silicon nitride sintered bodies having particularly excellent strength and creep resistance at high temperature, in which a total amount of MgO and Al.sub.2 O.sub.3 is more than 7% by weight and not more than 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 5-15 and the remainder is mainly Si.sub.3 N.sub.4 and at least one of magnesium sialon crystal represented by the general formula Mg.sub.x/2 Si.sub.6-y+x/2 Al.sub.y-x O.sub.y N.sub.8-y (0<x.ltoreq.y<8, preferably 0.9.ltoreq.x/y) and forsterite crystal represented by the formula Mg.sub.2 SiO.sub.4 is contained as a second phase in addition to the main crystal of Si.sub.3 N.sub.4, are produced by mixing a raw material powder of silicon nitride containing not greater than 2% by weight of oxygen with MgO and Al.sub.2 O.sub.3 so that a total amount of MgO and Al.sub.2 O.sub.3 is from 7% by weight to 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 5-15, and firing the resulting mixture at a temperature of 1,650.degree.-1,850.degree.

Abstract: Highly densified silicon nitride sintered bodies having excellent mechanical strength and oxidation resistance consist essentially of Si.sub.3 N.sub.4 and contain Y, Mg and Zr, in which a content of Si.sub.3 N.sub.4 is 95-70% by weight, a content of yttrium is 15-2% by weight calculated as Y.sub.2 O.sub.3, a content of magnesium is 15-0.5% by weight calculated as MgO and a content of zirconium is 13-0.5% by weight calculated as ZrO.sub.2 and are produced by forming a mixed raw powder consisting of 95-70% by weight of silicon nitride raw powder, yttrium compound of 15-2% by weight calculated as Y.sub.2 O.sub.3, magnesium compound of 15-0.5% by weight calculated as MgO and zirconium compound of 13-0.5% by weight calculated as ZrO.sub.2 into a shaped body, said yttrium compound, magnesium compound and zirconium compound being sintering aids, and firing the shaped body at a temperature of 1,650.degree.-1,800.degree. C. under ambient pressure in a nitrogen or an inert gas atmosphere.

Abstract: Silicon nitride sintered bodies having particularly excellent strength and creep resistance at high temperatures, in which a total amount of MgO and Al.sub.2 O.sub.3 is more than 6% by weight and not more than 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 4-19, with the remainder being mainly Si.sub.3 N.sub.4. At least one of crystalline magnesium sialon represented by the general formula Mg.sub.x/2 Si.sub.6-y+x/2 Al.sub.y-x O.sub.y N.sub.8-y (O<x.ltoreq.y<8, preferably 0.9.ltoreq.x/y) and crystalline forsterite represented by the formula Mg.sub.2 SiO.sub.4 is contained as a second phase in addition to the main crystal of Si.sub.3 N.sub.4. The sintered bodies are produced by mixing a raw material powder of silicon nitride containing less than 2% by weight of oxygen with MgO and Al.sub.2 O.sub.3 so that a total amount of MgO and Al.sub.2 O.sub.3 is from 6% by weight to 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.

Abstract: Silicon nitride sintered bodies having a high density, high mechanical strength and high fracture toughness, contain specific amounts of oxides or oxynitrides of Sr, Mg, a rare earth element and Zr respectively and the remainder being Si.sub.3 N.sub.4, are produced by shaping a raw batch material containing compounds of each of Sr, Mg, a rare earth element and Zr in given amounts, wherein Zr is added by abrasion of the grinding media and the mixture is pressurelessly sintered in nitrogen or an inert gas atmosphere.