Abstract: An aluminum nitride sintered body having resistance to plasma gas and high thermal conduction and having excellent optical properties. The aluminum nitride sintered body of the present invention is characterized in that the proportion of positrons which are annihilated within a period of 180 ps (picoseconds) in the aluminum nitride crystal, as determined in the defect analysis using a positron annihilation method, is not less than 90%, and the sintered body preferably has a thermal conductivity of not less than 200 W/mK.

Abstract: [Object] It is an object of the present invention to provide an aluminum nitride sintered body having resistance to plasma gas and high thermal conduction and having excellent optical properties. [Solution means] The aluminum nitride sintered body of the present invention is characterized in that the proportion of positrons which are annihilated within a period of 180 ps (picoseconds) in the aluminum nitride crystal, as determined in the defect analysis using a positron annihilation method, is not less than 90%, and the sintered body preferably has a thermal conductivity of not less than 200 W/mK.

Abstract: An aluminum nitride junction body useful as an electrostatic chuck for holding a semiconductor wafer in an apparatus for producing a semiconductor, comprising aluminum nitride sintered plates joined together via a sintered metal layer. When used in the above application, the junction structure works to uniformly adsorb the semiconductor wafer. The aluminum nitride junction body is obtained by joining aluminum nitride sintered plates 1-a and 1-b together having a sintered metal layer 2 of tungsten or molybdenum of a thickness of 15 to 100 ?m formed on at least a portion of the junction surface thereof, the sintered metal layer having a sheet resistivity of not larger than 1 ?/? and warping by not more than 100?/100 mm.

Abstract: An aluminum nitride sintered body having an oxygen concentration of not larger than 400 ppm, a metal impurity concentration of not larger than 150 ppm, and a carbon concentration of not larger than 200 ppm, and having an average crystal grain size of 2 ?m to 20 ?m. The sintered body exhibits particularly excellent optical properties such as an inclination of a spectral curve in the wavelength region of 260 to 300 nm of not smaller than 1.0 (%/nm), a light transmission factor of not smaller than 86% in the wavelength region of 400 to 800 nm, and a wavelength of not longer than 400 nm when the light transmission factor reaches 60% in the spectrum.

Abstract: An aluminum nitride sintered body having an oxygen concentration of not larger than 400 ppm, a metal impurity concentration of not larger than 150 ppm, and a carbon concentration of not larger than 200 ppm, and having an average crystal grain size of 2 ?m to 20 ?m. The sintered body exhibits particularly excellent optical properties such as an inclination of a spectral curve in the wavelength region of 260 to 300 nm of not smaller than 1.0 (%/nm), a light transmission factor of not smaller than 86% in the wavelength region of 400 to 800 nm, and a wavelength of not longer than 400 nm when the light transmission factor reaches 60% in the spectrum.

Abstract: A heat sink including a substrate of insulating ceramic and, superimposed on its upper surface, a diamond film for disposing an element thereon. The heat sink has excellent heat radiation characteristics and is stable during use. This heat sink is obtained by providing a substrate of ceramic containing aluminum nitride of high thermal conductivity as a principal component; forming on the substrate a bonding member layer, such as a silicon film which is capable of being bonded with the substrate and a diamond film; and forming a polycrystalline diamond film of high quality on the bonding member layer so that the polycrystalline diamond film is strongly bonded with the substrate via the bonding member layer interposed therebetween in accordance with, for example, the vapor phase method.

Abstract: Disclosed herein is a heat sink comprising a substrate of insulating ceramic and, superimposed on its upper surface, a diamond film for disposing an element thereon, which heat sink is excellent in heat radiation characteristics and can be stably used. This heat sink is obtained by providing a substrate of ceramic containing aluminum nitride of high thermal conductivity as a principal component; forming on the substrate a bonding member layer, such as a silicon film which is capable of being bonded with the substrate and a diamond film; and forming a polycrystalline diamond film of high quality on the bonding member layer so that the polycrystalline diamond film is strongly bonded with the substrate via the bonding member layer interposed therebetween in accordance with, for example, the vapor phase method.

Abstract: A pyrimidine compound of the formula [I] ##STR1## wherein R1 is H, C.sub.1 -C.sub.4 lower alkyl, halogen atom, --OH, C.sub.1 -C.sub.4 lower alkoxy, C.sub.1 -C.sub.6 hydroxy(lower)alkoxy or --NH.sub.2 ; R2 is H, --NH.sub.2 or --NHCOCH.sub.3 ; R3 is --NR5(CH.sub.2)i--CH.sub.2 OH; R4 is H, halogen atom, --NH.sub.2, --CN, --CHO, --CH.sub.2 OH, --COOH, --CH.sub.2 NH.sub.2, --CONH.sub.2 or --CH.dbd.N--A wherein A is --OH, C.sub.1 -C.sub.4 lower alkyl or C.sub.1 -C.sub.4 lower alkoxy; R5 is H or C.sub.1 -C.sub.4 lower alkyl; and i is an integer of 1 to 4, and an anti-rotavirus agent comprising, as an active ingredient, a compound of the formula [I] wherein R3 is a group selected from the following: ##STR2## The novel pyrimidine compound of the present invention and related derivatives thereof have superior anti-rotavirus action and are useful for the prophylaxis and treatment of rotaviral diseases.