Morphology and crystallography of the formation of small segregates in Czochralski grown calcium gallium germanium garnet are studied using TEM and STEM. Based on the observations, the following model has been developed for the formation of these defects. Evaporative loss of Ge from the melt during the crystal growth and the resulting local deviations from stoichiometry lead to random nucleation of small plate‐like precipitates, rich in Ga. As these precipitates grow, strain field interaction leads first to the formation of three‐dimensional segregates, and later to their alignment along the elastically soft ⟨100⟩ directions. Isolated segregates are also observed. Some of the segregates contain a central void filled with oxygen gas, while some others with or without a void have one or more dislocation loops around them. These segregates have the same garnet structure but a different chemical composition; they are rich in Ga and depleted in Ge. The model suggests that segregate‐free crystals can be grown by suppressing the evaporative loss of Ge from the melt during crystal growth.
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机译：使用TEM和STEM研究了直拉生长的钙镓锗石榴石中小偏析物形成的形态学和晶体学。根据这些观察结果，已经开发了以下模型来形成这些缺陷。在晶体生长过程中，熔体中 Ge 的蒸发损失以及由此产生的与化学计量的局部偏差导致富含 Ga、小板状沉淀物的随机成核。随着这些沉淀物的生长，应变场相互作用首先导致三维分离物的形成，然后导致它们沿着弹性柔软的〈100〉方向排列。还观察到孤立的分离。一些分离物包含一个充满氧气的中央空隙，而其他一些有或没有空隙的分离物周围有一个或多个位错环。这些偏析物具有相同的石榴石结构，但化学成分不同;它们富含 Ga，而 Ge 则枯竭。该模型表明，通过抑制晶体生长过程中熔体中 Ge 的蒸发损失，可以生长出无隔离和无连字符的晶体。
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