Low-Angle Grain-Boundary Macrostructure in Large-Diameter Czochralski White Sapphire |
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Authors: | V. F. S. YIP C. D. BRANDLE |
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Affiliation: | Union Carbide Corporation, Crystal Products Department, San Diego, California 92123 |
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Abstract: | Large-diameter Czochralski sapphire crystals grown in several orientations were occasionally found to contain complex networks of low-angle grain boundaries. The subboundaries lie in major low-index crystallographic planes which are uniquely determined by the gowth orientation. The major subboundary planes were the (11¯00) and (011¯0) for crystals gro_wn_in the direction normal to the ( r )-(1¯012) plane and the (1¯21¯0) and (21¯1¯0) planes for crystals grown in the 90°-[1120] direction. The formation of the subboundary macrostructure was attributed to an excessive temperature gradient during seeding and is not related to growth rate, impurity content, or annealing. |
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