Abstract: A ceramic sintered body comprising from 90 to 99.8% by volume of cordierite and from 0.2 to 10% by volume of mullite based on 100% by weight of a total sum of the contents of the cordierite and the mullite, and having a density of 2.48 g/cm3 or more.

Abstract: An intermediate substrate comprising: an intermediate substrate body containing an insulating material, and having a first face to be mounted with an semiconductor element and a second face opposing to said first face; and a semiconductor element mounting area including a plurality of first face terminals arranged on said first face, and being surrounded by an outermost periphery of said plurality of first face terminals, wherein a center of said semiconductor element mounting area is eccentric with respect to a center of said first face.

Abstract: A sintered alumina ceramic obtained by preparing a raw material powder mixture containing alumina and a Group 3A metal oxide or a Group 3A metal compound which provides a Group 3A metal oxide on heating, and firing said raw material powder mixture. The sintered ceramic contains alumina particles having an average particle diameter of 4.0 &mgr;m or smaller. In the sintered ceramic, the total content of alkali metal elements, alkaline earth metal elements, Si, and Ti as converted to oxides accounts for 0.1 mol or less with respect to 100 mols of alumina, the total peak intensity for the principal peaks for ReAlO3 and Re3Al5O12 (Re: Group 3A metal) amounts to from 1 to 75% of the intensity of the principal peak of alumina as measured by X-ray diffraction, and the relative density is 99.0% or higher with respect to the theoretical density.

Abstract: A ceramic sintered body comprising from 90 to 99.8% by volume of cordierite and from 0.2 to 10% by volume of mullite based on 100% by weight of a total sum of the contents of the cordierite and the mullite, and having a density of 2.48 g/cm3 or more.

Abstract: A sintered alumina ceramic obtained by preparing a raw material powder mixture containing alumina and a Group 3A metal oxide or a Group 3A metal compound which provides a Group 3A metal oxide on heating, and firing said raw material powder mixture. The sintered ceramic contains alumina particles having an average particle diameter of 4.0 &mgr;m or smaller. In the sintered ceramic, the total content of alkali metal elements, alkaline earth metal elements, Si, and Ti as converted to oxides accounts for 0.1 mol or less with respect to 100 mols of alumina, the total peak intensity for the principal peaks for ReAlO3 and Re3Al5O12 (Re: Group 3A metal) amounts to from 1 to 75% of the intensity of the principal peak of alumina as measured by X-ray diffraction, and the relative density is 99.0% or higher with respect to the theoretical density.

Abstract: To provide a silicon nitride based sintered material having high strength and high hardness and superior in reliability, silicon nitride sintered material has a composition mainly composed of silicon nitride or Si--Al--O--N, and further comprises 0.5 to 3 wt % of a Mg component, calculated as MgO, and 3 to 10 wt % of a Yb component, calculated as Yb.sub.2 O.sub.3. As a secondary crystal phase, the material contains one or more of Yb.sub.2 Si.sub.3 N.sub.4 O.sub.3, Yb.sub.2 Si.sub.3 N.sub.2 O.sub.5 and Yb.sub.4 Si.sub.2 N.sub.2 O.sub.7. Silicon nitride or Si--Al--O--N comprises 20-50 vol % of needle-like crystals of the entire material.

Abstract: A silicon nitride sintered product comprises, in % by weight, 1 to 10% Mg, calculated as MgO, 1 to 10% Zr, calculated as ZrO.sub.2, 0.1 to 2.0% of at least one of Al, calculated as Al.sub.2 O.sub.3, Li, calculated as Li.sub.2 O, and Na, calculated as Na.sub.2 O, and the remainder being Si.sub.3 N.sub.4 and unavoidable impurities.