An aluminum nitride powder containing a very small amount of coarse particles. An aluminum nitride powder which provides a resin composition having high affinity for resins and high moisture resistance.

The aluminum nitride powder has a volume average particle diameter D50 of 0.5 to 7.0 m in particle size distribution measured with a laser diffraction scattering particle size distribution meter, a D90/D50 ratio of 1.3 to 3.5 and a BET specific surface area of 0.4 to 6.0 m.sup.2/g and classified by removing coarse particles whose particle diameter is more than 5 times as large as D90. When resin paste obtained from this aluminum nitride powder and a resin is measured with a grind gauge, the upper limit particle diameter at which a streak is produced is not more than 5 times as large as D90. Since the classified aluminum nitride powder is surface modified, the aluminum nitride powder which has high filling property in a resin and is excellent in the moisture resistance and insulating property of a resin composition is obtained.

In various embodiments, single-crystal aluminum nitride boules and substrates are formed from the vapor phase with controlled levels of impurities such as carbon. Single-crystal aluminum nitride may be heat treated via quasi-isothermal annealing and controlled cooling to improve its ultraviolet absorption coefficient and/or Urbach energy.

In various embodiments, single-crystal aluminum nitride boules and substrates have low Urbach energies and/or absorption coefficients at deep-ultraviolet wavelengths. The single-crystal aluminum nitride may function as a platform for the fabrication of light-emitting devices such as light-emitting diodes and lasers.

Aluminum nitride crystal particles, aluminum nitride powders containing the same, production processes for both of them, an organic polymer composition comprising the aluminum nitride crystal particles and a sintered body. Each of the aluminum nitride crystal particles has a flat octahedral shape in a direction where hexagonal faces are opposed to each other, which is composed of two opposed hexagonal faces and 6 rectangular faces, in which the average distance D between two opposed corners of each of the hexagonal faces is 3 to 110 m, the length L of the short side of each of the rectangular faces is 2 to 45 m, and L/D is 0.05 to 0.8; each of the hexagonal faces and each of the rectangular faces cross each other to form a curve without forming a single ridge; and the true destiny is 3.20 to 3.26 g/cm.sup.3.

Aluminum nitride crystal particles, aluminum nitride powders containing the same, production processes for both of them, an organic polymer composition comprising the aluminum nitride crystal particles and a sintered body. Each of the aluminum nitride crystal particles has a flat octahedral shape in a direction where hexagonal faces are opposed to each other, which is composed of two opposed hexagonal faces and 6 rectangular faces, in which the average distance D between two opposed corners of each of the hexagonal faces is 3 to 110 m, the length L of the short side of each of the rectangular faces is 2 to 45 m, and L/D is 0.05 to 0.8; each of the hexagonal faces and each of the rectangular faces cross each other to form a curve without forming a single ridge; and the true destiny is 3.20 to 3.26 g/cm.sup.3.

In various embodiments, single-crystal aluminum nitride boules and substrates are formed from the vapor phase with controlled levels of impurities such as carbon. Single-crystal aluminum nitride may be heat treated via quasi-isothermal annealing and controlled cooling to improve its ultraviolet absorption coefficient and/or Urbach energy.

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

A thermally conductive resin composition includes an epoxy resin and a thermally conductive powder. The thermally conductive powder includes aluminum nitride having a silicon-containing oxide coating on a surface thereof and another thermally conductive powder. The content of the epoxy resin is 1% by mass or more and 20% by mass or less based on the total amount of the thermally conductive resin composition. The content of the thermally conductive powder is 80% by mass or more and 99% by mass or less based on the total amount of the thermally conductive resin composition. The content of the aluminum nitride having a silicon-containing oxide coating on a surface thereof is 10% by mass or more and 70% by mass or less based on the total amount of the thermally conductive resin composition. The content of the other thermally conductive powder is 10% by mass or more and 89% by mass or less based on the total amount of the thermally conductive resin composition.

An object of the present invention is to provide a surface-modified inorganic nitride having excellent dispersibility. Furthermore, another object of the present invention is to provide a composition, a thermally conductive material, and a device with a thermally conductive layer which contain the surface-modified inorganic nitride. The surface-modified inorganic nitride of the present invention includes an inorganic nitride, and a compound which is represented by General Formula (I) and is adsorbed onto a surface of the inorganic nitride. ##STR00001##