PRODUCTION OF LITHIUM TANTALATE SINGLE CRYSTAL

摘要

PURPOSE:To decrease the fluctuation in the compsn. within crystal lots and between the lots and to obtain a titled single crystal having a prescribed crystal compsn. by using specific raw materials for growing the lithium tantalate single crystal and growing the single crystal by a pulling up method. CONSTITUTION:The raw material for growing the lithium tantalate single crystal having 0.937+ or -0.004 Li/Ta is used as the raw material for growing the lithium tantalate single crystal in the stage of growing the lithium tantalate single crystal by the pulling up method. The correlation between the initial melt (two sintered raw material compsn.) and the fluctuation in the Curie temp. of the crystal in each pulling up crystal is investigated by assuming that the crystal compsn. and the Curier temp. of the crystal correspond 1 to 1 near the congruent compsn. From the result thereof, the above-described process for producing the single crystal is based on the finding that the fluctuating width of the crystal compsn. decreases if the lithium tantalate powder or the raw material for growing the single crystal such as single crystal ingot having finally 0.937+ or -0.004 raw material compsn. ratio is used by estimating the true congruent compsn. at 0.9342 Li/Ta molar ratio and taking the actual record of the fluctuation in the production process for the single crystal into consideration.