Abstract: An aluminum nitride sintered body comprising aluminum nitride crystals belonging to a Wurtzite hexagonal crystal system wherein the 3 axes a, b and c of the unit lattice of the crystal are defined such that the ratio b/a of the lengths of the axes b and a is 1.000 near the center of the crystal grain and lies within the range 0.997-1.003 in the vicinity of the grain boundary phase. Aluminum nitride sintered body is produced by sintering a molded body of a raw material powder having aluminum and nitrogen as its principal components at a temperature of 1700.degree.-1900.degree. C. in a non-oxidizing atmosphere having a partial pressure of carbon monoxide or carbon of not more than 200 ppm and then cooling the sintered body to 1500.degree. C. or a lower temperature at a rate of 5.degree. C./min or less. The aluminum nitride sintered body has a greatly improved thermal conductivity and, therefore, is suitable for heat slingers, substrates or the like for semiconductor devices.

Abstract: An aluminum nitride sintered body has a high breakdown voltage for serving as a substrate material particularly suited to highly integrated circuits. The aluminum nitride sintered body contains titanium, which is included as a solid solute in the aluminum nitride crystal lattice in a weight ratio of at least 50 ppm and not more than 1000 ppm. The unpaired electron concentration in the sintered body as determined from an absorption spectrum of electron spin resonance is at least 1.times.10.sup.13 /g. At least 0.1 percent by weight and not more than 5.0 percent by weight, in terms of TiO.sub.2, of an oxy-nitride of titanium and aluminum exists in the aluminum nitride sintered body. The aluminum nitride sintered body has a breakdown voltage of 20 kV/mm. The sintered body is obtained by nitriding aluminum nitride raw material powder in a nitrogen atmosphere at a temperature of 800 to 1400.degree. C., adding an oxy-nitride of titanium thereto with a sintering assistant, and sintering the mixture.

Abstract: An aluminum nitride powder having a surface layer containing an oxynitride characterized in that the surface layer of the aluminum nitride particle contains an aluminum oxynitride which has an oxygen content of 5 to 75 mol % in terms of Al.sub.2 O.sub.3 /(Al.sub.2 O.sub.3 +AlN). The surface layer of the aluminum nitride powder may contain, besides the aluminum oxynitride, at least one other oxynitride selected from among oxynitrides of Mg, Ca, Ba, Ti, V, Cr, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ru, Hf, Ta, W, Li, B, Si, Y, Sc and rare metal elements and the aluminum oxynitride and at least one other oxynitride have a total oxygen content in the range of 10 to 75 mol % in terms of (3.times.oxygen amount)/(3.times.oxygen amount+nitrogen amount).

Abstract: An aluminum nitride sintered body has a high breakdown voltage for serving as a substrate material particularly suited to highly integrated circuits. The aluminum nitride sintered body contains titanium, which is included as a solid solute in the aluminum nitride crystal lattice in a weight ratio of at least 50 ppm and not more than 1000 ppm. The unpaired electron concentration in the sintered body as determined from an absorption spectrum of electron spin resonance is at least 1.times.10.sup.13 /g. At least 0.1 percent by weight and not more than 5.0 percent by weight, in terms of TiO.sub.2, of an oxy-nitride of titanium and aluminum exists in the aluminum nitride sintered body. The aluminum nitride sintered body has a breakdown voltage of 20 kV/mm. The sintered body is obtained by nitriding aluminum nitride raw material powder in a nitrogen atmosphere at a temperature of 800.degree. to 1400.degree. C., adding an oxy-nitride of titanium thereto with a sintering assistant, and sintering the mixture.