# US 9,751,775 B2 · Process for making high purity aluminum oxide

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- Number: US 9,751,775 B2
- Document ID: US9751775B2
- Status: Granted
- Kind: B2
- Application number: 14/652,161
- Filed: 2013-12-17
- Published: 2015-12-24
- Granted: 2017-09-05
- Earliest claimed: 2012-12-17
- Assignees: Polar Sapphire Ltd.
- Applicants: Polar Sapphire Ltd.
- Inventors: Scott Nichol
- Web page: https://patentgrep.com/patent/US9751775B2

## CPC

- C01F 7/42: Preparation of aluminium oxide or hydroxide from metallic aluminium, e.g. by oxidation
- C01F 7/30: Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
- C01F 7/441: by calcination
- C01F 7/56: Chlorides (containing fluorine C01F7/52)
- C30B 29/20: Aluminium oxides
- C30B 35/007: {Apparatus for preparing, pre-treating the source material to be used for crystal growth}
- C01P 2006/80: Compositional purity
- C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00})
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

A method comprising contacting high-purity acid, high-purity aluminum, and high-purity water to form a first solution in a heated non-contaminating vessel, wherein the aluminum is employed in at least a stoichiometric amount relative to the acid, heating the first solution in a non-contaminating container, to provide a mother liquor and solid aluminum salts, separating the solid aluminum salts from the mother liquor, heating the solid aluminum salts in a non-contaminating crucible, to provide alpha aluminum oxide, and, optionally, washing the alpha aluminum oxide with high-purity water after some or all of the heating of the solid aluminum salts to provide the alpha aluminum oxide.

## Claims

### Claim 1

A method comprising:
(a) in a heated non-contaminating vessel, contacting high-purity acid, high-purity aluminum and high-purity water to form a first solution, wherein the high-purity aluminum is employed in at least a stoichiometric amount relative to the acid;
(b) in a non-contaminating container, heating the first solution, to provide a mother liquor and solid aluminum salts;
(c) separating the solid aluminum salts from the mother liquor;
(d) in a non-contaminating crucible, heating the solid aluminum salts, to provide alpha aluminum oxide; and
(e) optionally washing the alpha aluminum oxide with high-purity water after some or all of the heating of step (d) to provide a washed alpha aluminum oxide, wherein one or both of the alpha aluminum oxide provided by the heating of step (d) or the washed alpha aluminum oxide provided by the washing of step (e) is at least about 99.99 wt % pure aluminum oxide.

### Claim 2 (depends on 1)

The method of claim 1, further comprising, after step (c):
(f) dissolving the solid aluminum salts in high-purity water or high-purity acid, and repeating steps (b) and (c) one or more times, to provide subsequent solid aluminum salts in a subsequent solution; and
(g) separating the subsequent solid aluminum salts from the subsequent solution;
wherein step (d) comprises heating the subsequent solid aluminum salts separated in step (g) to provide the alpha aluminum oxide.

### Claim 3 (depends on 1)

The method of claim 1, after step (a); (h) separating solids from the first solution to provide a filtered solution.

### Claim 4 (depends on 1)

The method of claim 1, wherein the high-purity aluminum is employed in a molar equivalent or in molar excess relative to the high-purity acid.

### Claim 5 (depends on 1)

The method of claim 1, wherein the alpha aluminum oxide comprises less than about 30 ppmw total metallic and alkyl impurities.

### Claim 6 (depends on 1)

The method of claim 1, wherein the alpha aluminum oxide comprises less than about 5 ppmw of each of Na, Si, Fe, Ca, K, and Mg and less than about 1 ppmw of each of Ti, Cu, and Cr.

### Claim 7 (depends on 1)

The method of claim 1, wherein the high-purity aluminum is at least about 99.98 wt. % pure aluminum.

### Claim 8 (depends on 1)

The method of claim 1, wherein the high-purity acid comprises less than about 1 ppmw of each of Na, Ca, Li, Fe, Zn, Cu, Ti, Cr, K and Mg.

### Claim 9 (depends on 1)

The method of claim 1, wherein the high-purity acid comprises less than about 0.2 ppmw metallic impurities.

### Claim 10 (depends on 1)

The method of claim 1, wherein the high-purity water is at least about 99.999 wt. % pure water.

### Claim 11 (depends on 1)

The method of claim 1, wherein the alpha aluminum oxide is obtained in a yield of at least about 90 molar percent, relative to the high-purity acid.

### Claim 12 (depends on 1)

The method of claim 1, further comprising venting the non-contaminating vessel with air during the contacting of the high-purity aluminum, the high-purity acid, and the high-purity water to dilute a hydrogen level in the vessel.

### Claim 13

A method comprising:
(a) contacting high-purity acid, high-purity aluminum, and high-purity water in a non-contaminating vessel to form a first solution;
(b) at least one of heating and gas injecting the first solution, to provide a mother liquor and solid aluminum salts;
(c) separating the solid aluminum salts from the mother liquor;
(d) heating the solid aluminum salts, to provide alpha aluminum oxide; and
(e) washing the alpha aluminum oxide, to provide washed alpha aluminum oxide,
wherein one or both of the alpha aluminum oxide provided by the heating of step (d) or the washed alpha aluminum oxide provided by the washing of step (e) is at least about 99.99 wt % pure aluminum oxide.

### Claim 14 (depends on 13)

The method of claim 13, wherein the first solution comprises first solids and a first liquid, the method further comprising, subsequent to step (a), (f) separating the first liquid from the first solids to provide a filtered first solution, wherein step (b) comprises at least one of heating and gas injecting the filtered first solution.

### Claim 15 (depends on 13)

The method of claim 13, further comprising:
subsequent to step (c) and before step (d), (g) dissolving the solid aluminum salts in water or acid, and repeating steps (b) and (c) one or more times, to provide subsequent solid aluminum salts in a subsequent solution; and
(h) separating the subsequent solid aluminum salts from the subsequent solution; wherein step (d) comprises heating the subsequent solid aluminum salts to provide the alpha aluminum oxide.

### Claim 16 (depends on 13)

The method of claim 13, wherein the high-purity aluminum is employed in a molar equivalent or in a molar excess, relative to the high-purity acid.

### Claim 17 (depends on 13)

The method of claim 13, wherein the alpha aluminum oxide comprises less than about 30 ppmw total metallic and alkyl impurities.

### Claim 18 (depends on 13)

The method of claim 13, wherein the high-purity aluminum is at least about 99.98 wt. % pure aluminum.

### Claim 19 (depends on 13)

The method of claim 13, wherein the high-purity acid comprises less than about 1 ppmw of each of Na, Ca, Li, Fe, Zn, Cu, Ti, Cr, K and Mg.

### Claim 20 (depends on 13)

The method of claim 13, wherein the high-purity water is at least about 99.999 wt. % pure water.

### Claim 21 (depends on 13)

The method of claim 13, wherein the alpha aluminum oxide is obtained in a yield of at least about 90 molar percent, relative to the high-purity acid.