| 摘要 |
A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential ( DELTA T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low DELTA T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large DELTA T sufficient to increase material transport between the zones and rapid crystallization. alpha -Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350 DEG C. stepwise with a DELTA T of 0.25 DEG -3 DEG C., increasing the DELTA T to about 50 DEG C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.
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