Abstract In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

中文翻译：

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Kyropoulos 工艺过程中功率历史对大型蓝宝石晶体形状和热应力的影响

摘要 在这项研究中，数值研究了功率历程对蓝宝石晶体形状和 Kyropoulos 工艺过程中热应力的影响。仿真结果表明，热应力强烈依赖于功率历史。还研究了用不同功率历程产生的所有生长阶段晶体中的热应力分布。结果表明，在晶体籽晶、高度弯曲的晶体表面和晶体-熔体界面附近发现了高 von Mises 应力区域。随着晶体在冠部膨胀，发生在晶体-熔体界面的最大热应力值显着增加。此后，随着晶体的延长，最大热应力会降低。当晶体-熔体界面靠近坩埚底部时，最大 von Mises 应力显着增强。最大 Von Mises 应力有两个明显的峰值，分别在冠部阶段末期和最终阶段，此时可形成裂纹缺陷。为了缓解这个问题，需要考虑不同的功率历史以优化工艺以在晶体中产生最低的热应力。发现最佳功率历史可显着降低牙冠阶段的热应力。考虑不同的功率历史以优化工艺以在晶体中产生最低的热应力。发现最佳功率历史可显着降低牙冠阶段的热应力。考虑不同的功率历史以优化工艺以在晶体中产生最低的热应力。发现最佳功率历史可显着降低牙冠阶段的热应力。