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EP-4741543-A2 - PRESSURE CONTAINER FOR CRYSTAL PRODUCTION

EP4741543A2EP 4741543 A2EP4741543 A2EP 4741543A2EP-4741543-A2

Abstract

The present invention relates to a pressure container for crystal production having excellent corrosion-resistance. This pressure container produces crystals within the container using a seed crystal, a mineralizer, a raw material, and ammonia in a super critical state and/or a sub-critical state as a solvent. The pressure container has Ag present over the entire surface of at least the exposed inner surface thereof. The Ag can be disposed by one or a combination of two or more among, for instance, Ag lining, Ag welding, and Ag plating. The mineralizer is preferably a fluorine mineralizer containing no halogen atoms other than fluorine.

Inventors

  • KURIMOTO, KOUHEI
  • BAO, QUANXI
  • UEDA, MUTSUO
  • SASAGAWA, YUJI
  • MORIMOTO, MASAYA
  • ISHIGURO, TORU
  • CHICHIBU, SHIGEFUSA

Assignees

  • Japan Steel Works M&E, Inc.
  • Tohoku University

Dates

Publication Date
20260513
Application Date
20180405

Claims (10)

  1. A pressure container (1, 1A, 2, 2A, 3, 3A) for crystal production, the pressure container (1, 1A, 2, 2A, 3, 3A) being configured to produce a crystal using ammonia in a supercritical state and/or a subcritical state as a solvent, a raw material, a mineralizer, and a seed crystal inside the container, wherein the pressure container (1, 1A, 2, 2A, 3, 3A) comprises: a pressure container main body (10, 20) having an opening (100); a cover (11) configured to close the opening (100) of the pressure container main body (10, 20); and a gasket (12) disposed in a gap between the pressure container main body (10, 20) and the cover (11), characterized in that Ag is present at least on the gasket (12), and Ag plating (16B) is applied to an entire surface of the gasket (12).
  2. The pressure container for crystal production according to claim 1, wherein Ag is present at least on: an inner surface of the pressure container main body (10, 20) on which an Ag liner (14) is disposed; and an inner surface of the cover (11), to which Ag plating (16C) is applied.
  3. The pressure container for crystal production according to claim 1 or 2, wherein the pressure container is adapted for a nitride crystal.
  4. The pressure container for crystal production according to any one of claims 1 to 3, wherein the mineralizer is a fluorine-based mineralizer and does not contain a halogen atom other than fluorine.
  5. The pressure container for crystal production according to any one of claims 1 to 4, wherein the pressure container main body has a cylindrical shape, and the Ag liner having a bottomed cylindrical shape and having an opening is disposed on an inner surface of the pressure container main body.
  6. The pressure container for crystal production according to any one of claims 2 to 5, wherein the Ag liner (14) is installed up to a mouth part (101) of the pressure container main body (10, 20) and has a thickness of from 0.5 mm to 20 mm.
  7. The pressure container for crystal production according to any one of claims 2 to 6, wherein the Ag welding (15) joins an upper portion of an opening of the Ag liner (14) and the pressure container main body (10, 20) to seal a gap between the Ag liner (14) and the pressure container main body (10, 20).
  8. The pressure container for crystal production according to any one of claims 2 to 7, wherein an Ag plating layer formed by the Ag plating (16B, 16C) has a thickness of from 10 µm to 1000 µm.
  9. The pressure container for crystal production according to any one of claims 1 to 8, wherein the pressure container main body (10, 20) and the cover (11) are formed of a Ni-based alloy, an iron alloy, and/or a cobalt-based alloy.
  10. The pressure container for crystal production according to any one of claims 2 to 9, wherein a bottom of the pressure container main body (10, 20) has a bottom opening and a Bridgman seal (19) is inserted into the bottom opening, and wherein a member (18A) is provided on an upper side of the Bridgman seal (19) so as to surround a lower end portion of the Ag liner (14).

Description

TECHNICAL FIELD The present invention relates to a pressure container for crystal production using ammonia in a supercritical state and/or subcritical state as a solvent, a raw material, a mineralizer, and seed crystal. BACKGROUND ART An ammonothermal method is a crystal production method using ammonia in a supercritical or subcritical state as a solvent, and is particularly known as a method useful for producing nitride crystal of group 13 element in the periodic table with high purity. In production with this method, a solvent, a raw material, and a seed crystal are put in a pressure container for crystal production and the pressure container for crystal production is sealed, and a high temperature area and a low temperature area are formed by heating the pressure container for crystal production, a difference in temperature causes the raw material dissolved in the solvent to be recrystallized on the seed crystal. For example, a desired crystal can be produced by dissolving GaN polycrystal which is a raw material in supercritical ammonia and recrystallizing the GaN polycrystal on a GaN single crystal which is a seed crystal. Since the raw material such as GaN has extremely low solubility with respect to ammonia in the critical or subcritical state, a mineralizer is added to improve the solubility and promote crystal growth. The mineralizers are classified into acid mineralizers represented by ammonium halide (NH4X, X = F, Cl, Br, I) and basic mineralizers represented by alkali amide (NH2 X, X = Li, Na, K). An ammonia environment in the supercritical or subcritical state containing mineralizer is a very severe corrosive environment, and there are problems such as deterioration of container safety and contamination of metal impurities into the produced crystal due to corrosion of container structure materials. As measures against the above problems, it has been proposed to use another material excellent in corrosion resistance as a corrosion resistant portion on the inner surface of the pressure container in contact with the solvent, or to use a reaction container such as a capsule inside the pressure container in some cases. For example, in PTL 1 to 3, a Ni-based alloy is used as a material of the corrosion resistant portion. In PTL 4, the fluorine-containing film is used as a corrosion resistant portion. In PTL 5, a capsule of a malleable metal such as Au, Ag, Cu, or Pt is used as a corrosion resistant portion. In PTL 6, Pt, Ir, Pt-Ir alloy or the like are used as a corrosion resistant portion. In PTL 7, Pt, Ir, Au, Ti, V, Zr, Nb, Ta, W and alloys thereof are used as a corrosion resistant portion. In PTL 8, it is preferable to line or coat a part in contact with ammonia other than a shield portion with a noble metal, and examples of the noble metal include platinum (Pt), gold (Au), iridium (Ir), ruthenium (Ru), rhodium (Rh), palladium (Pd), rhenium (Re), silver (Ag), and alloys having these elements as a main component. Among them, platinum, iridium, or an alloy thereof is considered to be preferable in view of excellence in corrosion resistance. CITATION LIST PATENT LITERATURE PTL 1: JP-A-2007-56320PTL 2: JP-A-2010-222247PTL 3: JP-A-2015-140288PTL 4: JP-A-2013-203652PTL 5: JP-T-2006-513122PTL 6: JP-A-2006-193355PTL 7: JP-A-2012-017212PTL 8: JP-T-2012-176318 SUMMARY OF INVENTION TECHNICAL PROBLEM However, in a case of the Ni-based alloys and fluorine-containing film of PTL 1 to 4, the corrosion in the ammonia environment including the mineralizer cannot be sufficiently prevented. In a case where a capsule of a malleable metal such as Au, Ag, Cu, or Pt disclosed in PTL 5 is used as a corrosion resistant portion, there is a problem in that since the metals are soft and thus the capsule is deformed, it cannot be used repeatedly for a long period of time. In PTL 6 to 8, although Pt or Ir liners are mainly used as a corrosion resistant material and can prevent the corrosion in the ammonia environment including the mineralizer, Pt is expensive, thereby leading to an increase in container production cost. In addition, it is clear that Pt forms a reaction layer by alloying with Ga, and there is a risk of becoming brittle and breaking in use for a long period of time. Also, no specific use has been described for other noble metals. An object of the present invention is to solve the problems in the related art as described above, and there is provided a pressure container for crystal production which has high corrosion resistance and can be used repeatedly for a long period of time. SOLUTION TO PROBLEM The pressure container for crystal production according to the present invention is as specified in claim 1. Preferred embodiments thereof are specified in the dependent claims. ADVANTAGEOUS EFFECTS OF INVENTION As described above, according to the present invention, when Ag is present on the entire surface of at least the exposed inner surface of the pressure container, the corrosion of the inner surface of the pres