METHOD FOR PRODUCTION OF SINGLE CRYSTAL LITHIUM ALUMINATE Russian patent published in 2005 - IPC

FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO₂ is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700^oC in the first step and at 1050^oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg