Abstract: Provided is a method for producing, with a small amount of lithium, a hexagonal boron nitride powder containing thick hexagonal boron nitride particles. A method for producing a hexagonal boron nitride powder, including the steps of: preparing a mixed powder which contains an organic compound containing nitrogen atoms, a boron source which contains boron atoms whose molar ratio with respect to the nitrogen atoms is adjusted to be 0.26 or more and 0.67 or less, and an alkali metal in which lithium atoms are adjusted to be in a range of 30 mol % or more and less than 100 mol %, the alkali metal being present such that a molar ratio of the boron atoms with respect to alkali metal atoms contained in the alkali metal is 0.75 or more and 3.35 or less; and heating the mixed powder at a maximum temperature of 1200° C. or higher and 1500° C. or lower.

Abstract: Provided is a production method which makes it possible to improve a filling property, with respect to a resin, of a hexagonal boron nitride powder which contains hexagonal boron nitride particles each having a low aspect ratio, while maintaining low thermal conduction anisotropy of the hexagonal boron nitride powder. A method of producing a hexagonal boron nitride powder includes disintegrating, by a means which substantially does not involve pulverization of primary particles, a hexagonal boron nitride raw material powder which contains (i) hexagonal boron nitride particles each having an aspect ratio of 1.5 to 5.0 and (ii) an aggregate that contains hexagonal boron nitride particles each having an aspect ratio of more than 5.0.

Abstract: It is an object to achieve a resin sheet having high thermal conductance and high dielectric strength. Hexagonal boron nitride powder in accordance with an aspect of the present invention includes hexagonal boron nitride agglomerate particles each including agglomerated hexagonal boron nitride primary particles, and has a specific surface area of not less than 0.5 m2/g and not more than 5.0 m2/g. The hexagonal boron nitride primary particles each have a long diameter of not less than 0.6 ?m and not more than 4.0 ?m and an aspect ratio of not less than 1.5 and not more than 5.0.

Abstract: To provide an aluminum nitride particle having a hexagonal columnar barrel part and bowl-like projection parts at both ends of the columnar part, wherein the long diameter (D) of the barrel part is 10 to 250 ?m, the ratio (L1/D) of the distance (L1) between the apexes of the two projection pars to the long diameter (D) of the barrel part is 0.7 to 1.3, and the percentage of the length or thickness (L2) of the barrel part to the distance (L1) between the apexes of the two projection parts is 10 to 60%. The aluminum nitride particle can provide high heat conductivity and excellent electric insulation to a resin when it is filled into the resin.

Abstract: To provide an aluminum nitride particle having a hexagonal columnar barrel part and bowl-like projection parts at both ends of the columnar part, wherein the long diameter (D) of the barrel part is 10 to 250 ?m, the ratio (L1/D) of the distance (L1) between the apexes of the two projection pars to the long diameter (D) of the barrel part is 0.7 to 1.3, and the percentage of the length or thickness (L2) of the barrel part to the distance (L1) between the apexes of the two projection parts is 10 to 60%. The aluminum nitride particle can provide high heat conductivity and excellent electric insulation to a resin when it is filled into the resin.

Abstract: A metal fluoride single crystal pulling apparatus that upward pulling initiation through termination, in the state of shallow melt capable of highly effective inhibition of scatterer formation, can perform stable growth of single crystal and can suppress any mixing of air bubbles and occurrence of crystal break during crystal growth, etc; and a process for producing a metal fluoride single crystal therewith. As a crucible for accommodating a melt of raw metal fluoride, use is made of a double structured crucible composed of an outer crucible and an inner crucible. In the upward pulling of single crystal, the accommodation depth of inner crucible relative to the outer crucible is increased in accordance with any decrease of melt accommodated in the inner crucible according to the growth of single crystal, so that the melt accommodated in the outer crucible is fed into the inner crucible to thereby maintain the amount of melt accommodated in the inner crucible within a given range.

Abstract: Disclosed is a method for producing a BaLiF3 single crystal by a melt growth method, wherein a raw material melt for said single crystal comprising BaF2, LiF and MgF2 in such amounts that the Ba/(Ba+Li+Mg) ratio by mol is in the range of 0.35 to 0.48 and the Mg/(Li+Mg) ratio by mol is in the range of 0.001 to 0.03. In the case where a BaLiF3 single crystal that is useful as a last lens of immersion exposure tools for producing a semiconductor is produced by a melt growth method using, as a raw material, a melt containing excess Li, the Li component is liable to be precipitated to make the resulting BaLiF3 single crystal opaque, and the light transmittance is deteriorated, but such problems can be solved by the present invention.

Abstract: A single crystal of alkaline earth metal fluoride is produced by a single crystal pulling method, has a straight barrel part diameter of not less than 17 cm, preferably has a straight barrel part length of not less than 5 cm, and has a light transmittance, as measured at a wavelength of 632.8 nm, of not less than 80%, preferably 90 to 98%. Further, the main crystal growth plane of the single crystal is the {111} plane or the {100} plane. The single crystal of alkaline earth metal fluoride has a large diameter as described above, and in spite that it is in an as-grown state, the peripheral surface is not opaque and the visible light transmittance is high. Therefore, evaluation of bubbles or inclusions in the crystal becomes feasible without performing complicated machining of the crystal, and from the single crystal, a large-sized optical material having advantageous properties such as high quality and high uniformity can be cut out.

Abstract: A metal fluoride single crystal pulling apparatus that upward pulling initiation through termination, in the state of shallow melt capable of highly effective inhibition of scatterer formation, can perform stable growth of single crystal and can suppress any mixing of air bubbles and occurrence of crystal break during crystal growth, etc; and a process for producing a metal fluoride single crystal therewith. As a crucible for accommodating a melt of raw metal fluoride, use is made of a double structured crucible composed of an outer crucible and an inner crucible. In the upward pulling of single crystal, the accommodation depth of inner crucible relative to the outer crucible is increased in accordance with any decrease of melt accommodated in the inner crucible according to the growth of single crystal, so that the melt accommodated in the outer crucible is fed into the inner crucible to thereby maintain the amount of melt accommodated in the inner crucible within a given range.

Abstract: A last lens for immersion lithography exposure equipment, composed of a crystal represented by formula BaLiF3. The crystal is preferably a single crystal represented by formula BaLiF3. The immersion lithography exposure equipment preferably comprises a light source which emits light with a wavelength of not more than 200 nm. More specifically, the immersion lithography exposure equipment preferably comprises an ArF excimer laser oscillator or an F2 excimer laser oscillator. In the last lens for the immersion lithography exposure equipment, at the wavelength of light used in a light source, preferably at a wavelength of not more than 200 nm, a high refractive index, a high transmission, and low SBR can be realized, and the resolution of the exposure equipment can easily be improved.

Abstract: A single crystal pulling apparatus for a metal fluoride comprising a crucible provided in a chamber for filling with a molten solution of a single crystal material, a melting heater provided to surround the crucible, a vertically movable single crystal pulling bar for attaching a seed crystal on a tip thereof for coming in contact with the molten solution of the single crystal material in the crucible, a heat insulating wall provided in the chamber to surround at least a peripheral side portion of a single crystal pulling region in an upper part of the crucible, a ceiling board for closing an opening portion of an upper end in an upper part of the heat insulating wall, and a single crystal pulling chamber surrounded by the heat insulating wall and the ceiling board, wherein the ceiling board is provided with at least an inserting hole for inserting the single crystal pulling bar, and wherein a coefficient of thermal conductivity in a direction of a thickness of the ceiling board is 1000 to 50000 W/m2·K.

Abstract: The single crystal of alkaline earth metal fluoride of the invention is produced by a single crystal pulling method, has a straight barrel part diameter of not less than 17 cm, preferably has a straight barrel part length of not less than 5 cm, and has a light transmittance, as measured at a wavelength of 632.8 nm, of not less than 80%, preferably 90 to 98%. Further, the main crystal growth plane of the single crystal of the invention is the {111}plane or the {100}plane. The single crystal of alkaline earth metal fluoride of the invention has a large diameter as described above, and in spite that it is in an as-grown state, the peripheral surface is not opaque and the visible light transmittance is high. Therefore, evaluation of bubbles or inclusions in the crystal becomes feasible without performing complicated machining of the crystal, and from the single crystal, a large-sized optical material having advantageous properties such as high quality and high uniformity can be cut out.

Abstract: A single crystal pulling apparatus for a metal fluoride comprising a crucible provided in a chamber and filling a molten solution of a single crystal manufacturing material, a melting heater provided to surround the crucible, a vertically movable single crystal pulling bar including a seed crystal on a tip and coming in contact with the molten solution of the single crystal manufacturing material filled in the crucible, a heat insulating wall provided in the chamber to surround at least a peripheral side portion of a single crystal pulling region in an upper part of the crucible, a ceiling board for closing an opening portion of an upper end in an upper part of the heat insulating wall, and a single crystal pulling chamber surrounded by the heat insulating wall and the ceiling board, wherein the ceiling board is provided with at least an inserting hole for inserting the single crystal pulling bar, and a coefficient of thermal conductivity in a direction of a thickness of the ceiling board is 1000 to 50000 W/m

Abstract: The object of the present invention is to provide an as-grown single crystal of calcium fluoride having a large diameter and small birefringence. The as-grown single crystal of calcium fluoride according to the present invention is obtained by a single crystal pulling method (Czochralski method), has a straight barrel part diameter of 17 cm or more, preferably has a straight barrel part length of 50 mm or more, and has a birefringence of not more than 3 nm/cm, preferably 0.1 to 2.0 nm/cm.