Material strength study on cracking of oxide bulk single crystals for optelectronic use

光电用氧化物块体单晶的开裂材料强度研究

基本信息

批准号：
04650089
负责人：
MIYAZAKI Noriyuki
金额：
$ 1.34万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650089/
关键词：
Oxide Single Crystal Czochralski Growth Thermal Stress Finite Element Method Thermal Expansion Coefficient Elastic constants Anisotropy Cracking CZ法異片性

项目摘要

Oxide single crystals such as LiNbO_3(LN) and LiTaO_3(LT) are used as optelectronic materials. Such bulk single crystals are manufactured by the Czochralski growth method. Macroscopic cracking sometimes occurs during growth process. Such cracking would be caused by thermal stress in a single crystal. In the present study, a finite element computer program was developed for the thermal stress analysis of trigonal single crystals such as LN and LT.A tensor transformation technique was used to obtain the elastic constant matrix and the thermal expansion coefficient vector corresponding to an arbitrary pulling direction, and they are incorporated into the finite element program. Using this program, we analyzed the thermal stress in LN bulk single crystals, which were grown in a pulling apparatus in Institute for Materials Research, Tohoku University. The temperature boundary conditions of the crystals were obtained from the heat conduction analysis of the global system. Thermal stress analyzes were performed for the pulling directions of both the a-axis and the c-axis. The results show that the maximum thermal stress is lower in the c-axis pulling than in the a-axis pulling, which indicates that the a-axis pulling is easier to crack than the c-axis pulling. It is also found that a lower stress region spreads widely in the bulk single crystal pulled in the a-axis direction. This predicts that the a-axis pulling could provide a bulk single crystal of higher quality than the c-axis pulling, if macroscopic cracking can be prevented. This prediction was verified by observing microscopic defects in a single crystal obtained by the a-axis pulling.In order to study the cracking of LN single crystals quantitatively, thermal shock experiments were carried out using circular disk speciments. The experimental results show that the cracking mainly occurs at the cleavage planes, which indicates that the stresses normal to the cleavage planes would induce the cracking.

氧化物单晶（例如Linbo_3（LN）和Litao_3（LT））用作Optelectronic材料。这种大量的单晶是通过Czochralski生长法制造的。宏观裂纹有时在生长过程中发生。这种破裂将是由单晶中的热应力引起的。在本研究中，开发了有限元计算机程序，用于对三角晶体的热应力分析，例如LN和LT。一种张量转换技术来获得弹性恒定矩阵以及与任意拉动方向相对应的热膨胀系数矢量，并将其纳入有限元元素程序中。使用该程序，我们分析了Tohoku University材料研究所的拉动设备中生长的LN散装单晶的热应力。晶体的温度边界条件是从全球系统的热传导分析中获得的。对A轴和C轴的拉力方向进行了热应力分析。结果表明，C轴拉的最大热应力比A轴拉动较低，这表明与C轴拉动相比，A轴拉动更容易裂纹。还发现，较低的应力区域在A轴方向上拉动的散装单晶中广泛扩散。这预测，如果可以防止宏观的裂纹，则A轴拉动可以提供比C轴拉的大量单晶。通过观察通过A轴拉的单晶体中的显微镜缺陷来验证了这一预测。在数量上研究LN单晶体的裂纹，使用圆盘样品进行了热休克实验。实验结果表明，裂纹主要发生在裂解平面上，这表明与裂解平面的正常应力会诱导裂纹。