Abstract: Black sintered bodies of aluminum nitride are produced by adding a sintering aid selected from the group consisting of (a) an oxide mixture of calcium oxide and at least one of tungsten oxide and molybdenum oxide, (b) an oxide containing calcium and at least one of tungsten and molybdenum and (c) a mixture of compounds capable of being converted into said oxide mixture (a) or said oxide (b) by sintering to aluminum nitride so that the resulting composition consists essentially of 0.1 to 20 wt. % in the total amount (calculated as oxides of Ca, W and Mo) of the sintering aid and balance aluminum nitride, molding the composition and sintering the molded composition at relatively low temperature. The black sintered bodies thus obtained are especially useful as materials for insulating substrate, heat sink and packaging for semiconductor device due to their high density, good thermal conductivity and superior light-shielding ability.

Abstract: Sintered bodies of aluminum nitride are produced by adding, as a sintering aid, an oxide mixture consisting essentially of calcium oxide, yttrium oxide and one or more oxides of tungsten oxide and molybdenum oxide or a mixture of compounds (precursors) capable of being converted into said oxide mixture by firing to aluminum nitride as a main component in such proportions that total amounts of the sintering aid is in the range 0.1 to 20% by weight (calculated as oxides of CaO, Y.sub.2 O.sub.3, WO.sub.3 and MoO.sub.3) based on the sum of the weight as the oxide forms of the sintering aid and aluminum nitride, molding the resulting composition and sintering the molded composition. The composition can be sintered at relatively low temperature. The black sintered bodies thus obtained are especially useful as materials for insulating substrate, heat sink, packaging for semiconductor device, etc. due to their high density and good thermal conductivity.