Abstract: A method for producing hexagonal boron nitride single crystals including mixing boron nitride crystals with a solvent thereby obtaining a mixture, heating and melting the mixture under high-temperature and high-pressure thereby obtaining a melted mixture, and recrystallizing the melted mixture thereby producing hexagonal boron nitride single crystals, wherein the solvent is boronitride of alkaline earth metal, or boronitride of alkali metal and the boronitride of alkaline earth metal.

Abstract: A method for producing hexagonal boron nitride single crystals including mixing boron nitride crystals with a solvent thereby obtaining a mixture, heating and melting the mixture under high-temperature and high-pressure thereby obtaining a melted mixture, and rectystallizing the melted mixture thereby producing hexagonal boron nitride single crystals, wherein the solvent is boronitride of alkali earth metal, or boronitride of alkali metal and the boronitride of alkali earth metal.

Abstract: A solid-state far ultraviolet light emitting element is formed by a hexagonal boron nitride single crystal, excited by electron beam irradiation to emit far ultraviolet light having a maximum light emission peak in a far ultraviolet region at a wavelength of 235 nm or shorter.

Abstract: While high-purity hexagonal boron nitride monocrystal (hBN) obtained by way of a high temperature/high-pressure treatment in the presence of a high-purity solvent has excellent properties in terms of far-UV luminescence characteristics, it has drawbacks including that it can be easily adversely affected by mechanical vibrations and impetus, that monocrystal shows a poor morphological retentiveness and that the luminescence characteristics fluctuate to shift the selected and set wavelength. The present invention can overcome the drawbacks of being easily affected by vibrations and showing a poor morphological retentiveness by grinding down the monocrystal obtained by a solvent/refining process into powder and applying the powder to a light emitting surface. Thus, the present invention provides crystal powder to be used for a far-UV luminescence device showing excellent luminescence characteristics that are stable and do not fluctuate.

Abstract: A solid-state far ultraviolet light emitting element is formed by a hexagonal boron nitride single crystal, excited by electron beam irradiation to emit far ultraviolet light having a maximum light emission peak in a far ultraviolet region at a wavelength of 235 nm or shorter.

Abstract: While high-purity hexagonal boron nitride monocrystal (hBN) obtained by way of a high temperature/high-pressure treatment in the presence of a high-purity solvent has excellent properties in terms of far-UV luminescence characteristics, it has drawbacks including that it can be easily adversely affected by mechanical vibrations and impetus, that monocrystal shows a poor morphological retentiveness and that the luminescence characteristics fluctuate to shift the selected and set wavelength. The present invention can overcome the drawbacks of being easily affected by vibrations and showing a poor morphological retentiveness by grinding down the monocrystal obtained by a solvent/refining process into powder and applying the powder to a light emitting surface. Thus, the present invention provides crystal powder to be used for a far-UV luminescence device showing excellent luminescence characteristics that are stable and do not fluctuate.

Abstract: A highly pure hexagonal boron nitride single crystal not influenced by impurities and capable of high-luminance short wave ultraviolet light emission reflecting inherent characteristics is provided; a high-luminance ultraviolet light emitting element is provided by using the above single crystal; and utilizing the above element, a simple compact low-cost long-lived far ultraviolet solid-state laser and far ultraviolet solid-state light emitting apparatus are provided. A highly pure hexagonal boron nitride single crystal having a single light emission peak in the far ultraviolet region of up to a wavelength of 235 nm is produced by melting said boron nitride crystal as raw material in the presence of a highly pure solvent under high-temperature and high-pressure, followed by crystallization. A light emitting element or a light emitting layer comprised of the obtained crystal is excited with electron beams, and the thus generated far ultraviolet light resonated or without resonation is taken out.