METHOD FOR PRODUCING ALPHA-ALUMINIUM OXIDE FOR SUBSEQUENT GROWTH OF SINGLE-CRYSTAL SAPPHIRE Russian patent published in 2021 - IPC C01F7/42 B01J19/12 C30B29/20 

FIELD: chemistry.

SUBSTANCE: present invention relates to the field of chemistry, namely, to a method for producing alpha-aluminum oxide for the subsequent growth of single-crystal sapphire. The method is characterized by the preliminary stage of oxidation of a particularly pure metal aluminum powder with air oxygen in a plasma generator flame at a temperature from 2040 to 3000°С to produce particles of fine gamma-aluminum oxide powder, followed by a stage of concentration of the resulting gamma-aluminum oxide powder on a pass-through electric filter using a high-voltage DC power source with a current strength from 0.2 to 0.5 A and a voltage from 15 to 20 kV, and a subsequent stage of compaction of gamma-aluminum oxide powder to a specific weight of 1 g/cm3. Further, the gamma-aluminum oxide is melted in an induction furnace at a temperature from 2050 to 3000°С in an electromagnetic field at a frequency from 700 to 800 kHz and a power from 120 to 150 kW, for 1.5 to 2 hours. A portion of the gamma aluminum oxide is pre-loaded into the furnace container, then at least one ring of high-purity aluminum metal is placed in it, which is necessary to initiate heating, followed by adding new portions of gamma aluminum oxide until the furnace container is completely filled with the melt, followed by cooling the melt at ambient temperature.

EFFECT: improved method for producing compact and high-purity aluminum oxide in the form of alpha-oxide, suitable for the production of single-crystal sapphire.

6 cl, 1 tbl, 3 dwg