Abstract: A process for producing a sintered body of aluminum nitride, which comprises mixing an aluminum nitride powder with (A) an alkaline earth metal aluminate, or both of (A-1) an oxide or oxide-forming compound of aluminum, and (A-2) an oxide or oxide-forming compound of an alkaline earth metal, and (B) an oxide or oxide-forming compound of yttrium or an element of the lanthanide series, and firing the resulting mixture.

Abstract: Aluminum nitride granules which are characterized in that (a) they are composed mainly of aluminum nitride, (b) their bulk density ranges from 0.5 to 1.5 g/cc, (c) the mean particle diameter thereof is within the range of 20 to 500 .mu.m, and (d) they have a breaking strength of 0.5 to 5.0 g. The aluminum nitride granules can be prepared by (1) mixing an aluminum nitride powder, a surfactant, a binder and an organic solvent, and optionally, at least one inorganic matter other than aluminum nitride, to form a slurry, (2) granulating the slurry, and (3) heating the resultant granulated particles to form the granules.

Abstract: A process for producing a sintered body of aluminum nitride, which comprises(1) forming a raw molded article from a homogeneous mixture of(A) a fine powder of aluminun nitride, and(B) a sintering aid composed substantially of (a) at least one halogen compound of at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium, and (b) at least one halogen-free compound of at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium; and(2) sintering the raw molded article at a temperature of 1600.degree. to 2100.degree. C. in a non-oxidizing atmosphere. A sintered body having a high thermal conductivity and a high density of at least 3.2 g/cm.sup.3 is prepared by the process.

Abstract: A process for producing a sintered body of aluminum nitride, which comprises mixing an aluminum nitride powder with (A) an alkaline earth metal aluminate, or both of (A-1) an oxide or oxide-forming compound of aluminum, and (A-2) an oxide or oxide-forming compound of an alkaline earth metal, and (B) an oxide or oxide-forming compound of yttrium or an element of the lanthanide series, and firing the resulting mixture.

Abstract: A fine powder of aluminum nitride having an average particle diameter of not more than 2 microns and comprising at least 94% by weight of aluminum nitride, at most 3% by weight of bound oxygen and at most 0.5% by weight as metal of metal compounds as impurities.The fine aluminum nitride powder is prepared from a fine alumina powder and a fine carbon powder as starting materials.The fine aluminum nitride powder provides a sintered body having a high purity and a high density such as at least 2.9 g/cm.sup.3.The fine aluminum nitride powder is also useful as a raw material for alpha-Sialon, beta-Sialon and AlN polytypes, as an addition aid in various ceramics.