A synthetic block for optimizing the performance of diamonds and gemstones is provided, including: a sealing material, a thermal insulation material, conductive materials, and a heating material. The conductive materials are provided at both ends of the sealing material. The heating material abuts between the conductive materials, and a high-temperature and high-pressure area is formed inside the heating material. The thermal insulation material includes a first thermal insulation tube and a second thermal insulation tube that are sequentially telescoped the conductive materials. The first thermal insulation tube abuts on an outer wall of the heating material, the second thermal insulation tube is provided between the sealing material and the first thermal insulation tube, a height of the second thermal insulation tube is greater than that of the first thermal insulation tube, and the synthetic block is square.

A synthetic block for optimizing the performance of diamonds and gemstones is provided, including: a sealing material, a thermal insulation material, conductive materials, and a heating material. The conductive materials are provided at both ends of the sealing material. The heating material abuts between the conductive materials, and a high-temperature and high-pressure area is formed inside the heating material. The thermal insulation material includes a first thermal insulation tube and a second thermal insulation tube that are sequentially telescoped the conductive materials. The first thermal insulation tube abuts on an outer wall of the heating material, the second thermal insulation tube is provided between the sealing material and the first thermal insulation tube, a height of the second thermal insulation tube is greater than that of the first thermal insulation tube, and the synthetic block is square.

An apparatus for processing materials at high temperatures comprises a high strength enclosure; a plurality of high strength radial segments disposed adjacent to and radially inward from the high strength enclosure; a liner disposed adjacent to and radially inward from the radical segments; a chamber defined interior to the liner; a heating device disposed within the chamber; and a capsule disposed within the chamber, the capsule configured to hold a supercritical fluid. The apparatus may be used for growing crystals, e.g., GaN, under high temperature and pressure conditions.

An object of the present invention is to manufacture single crystals of high quality on an industrial production scale by preventing impurities from being mixed in single crystals when the single crystals are produced by the solvothermal method. A pressure vessel body 1, in which a supercritical state is maintained, is made of heat resistant alloy, a portion of the pressure vessel body is open, a corrosion-resistant mechanical lining 5 is provided on an inner face of the pressure vessel and on an entire outer circumferential edge of the opening, and the opening is sealed by an airtight mating face formed out of a corrosion-resistant mechanical lining, which is formed on the outer circumferential edge of the opening, and by an airtight mating face of the corrosion-resistant mechanical lining cover 6 on an inner face of the cover 3 through a corrosion-resistant gasket member. Since the pressure vessel body and the inner face of the cover are covered with the corrosion-resistant mechanical lining, corrosion can be prevented. The corrosion-resistant mechanical lining ensures the sealing property on the airtight mating face between the pressure vessel body and the cover and further effectively prevents corrosion in the airtight sealing portion and it becomes possible to repeatedly open and close the airtight sealing portion.

A crystal has a diameter of 1 cm or more and shows a strongest peak in cathode luminescent spectrum at a wavelength of 360 nm in correspondence to a band edge.

A method of growing high-quality, group-III nitride, bulk single crystals. The group III-nitride bulk crystal is grown in an autoclave in supercritical ammonia using a source material or nutrient that is a group III-nitride polycrystals or group-III metal having a grain size of at least 10 microns or more and a seed crystal that is a group-III nitride single crystal. The group III-nitride polycrystals may be recycled from previous ammonothermal process after annealing in reducing gas at more then 600 C. The autoclave may include an internal chamber that is filled with ammonia, wherein the ammonia is released from the internal chamber into the autoclave when the ammonia attains a supercritical state after the heating of the autoclave, such that convection of the supercritical ammonia transfers source materials and deposits the transferred source materials onto seed crystals, but undissolved particles of the source materials are prevented from being transferred and deposited on the seed crystals.