Piezoerescence—the growth of Dauphiné twinning in quartz under stress
Piezoerescence—the growth of Dauphiné twinning in quartz under stress
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压电现象——应力作用下石英中多芬孪晶的生长
DOI：
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发表时间：
1951
期刊：
影响因子：
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通讯作者：
W. Wooster
中科院分区：
文献类型：
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作者：
L. A. Thomas;W. Wooster
已经发现，通过使α-石英样品经受由机械或热手段产生的应力，可以产生、改变或在某些情况下消除Dauphiné孪生。实验观察结果可以用一种可逆现象来解释，即在应力的影响下，一种晶体取向从另一种晶体取向中生长出来，为此提出了术语压致发光。石英板和条在通过外部手段扭曲或弯曲时，或在通过纵向温度梯度保持应变状态时，保持在约400° C。在一般情况下，所产生的孪晶边界，如酸蚀刻所示，近似于一个“理想”的孪晶图案，这是试样的晶体取向和所施加的应力的类型的特征。提出了一种压致发光理论，它依赖于这样的原理，即在进行处理的石英试样的任何部分，所开发的晶体取向是存储最大弹性能量的取向。这导致制定一个双弹性函数，这是成比例的弹性能量之间的差异，在恒定应力的两个部分的双。因此，如果在给定的应力系统下，孪晶取向的单位体积的弹性能大于母取向的弹性能，那么孪晶取向被晶体吸收;否则母取向保持不变。在一个给定的试样和适当的双弹性功能的主应力的知识，使“理想”的双晶图案在晶体的每一个部分被预测。在大多数实验中，预测的和实验观察到的孪晶图案之间是一致的，最大弹性能理论的基本特征似乎是合理的。对于石英等各向异性体，从外部施加的应力中很难估计晶体内任何点的主应力，而且除了孪生区的出现或不存在之外，还缺乏对压致发光的任何定量测量，这阻碍了对该理论的详细检验。另一个困难来自于某些样品中存在的阻碍压致发光的结构异常，在这方面，对这种现象的研究部分是对晶体完整性的研究。
It has been found that Dauphiné twinning can be created, modified or, in some instances, eliminated, by the subjection of α-quartz specimens to stress produced by mechanical or thermal means. The experimental observations can be explained in terms of a reversible phenomenon, the growth of one crystallographic orientation out of another under the influence of stress, for which the term piezocrescence is proposed. Plates and bars of quartz have been held at about 400° C while they were twisted or bent by external means or while they were kept in a state of strain by means of a lengthwise temperature gradient. In general, the resulting twin boundaries, as shown by acid etching, approximate to an ‘ideal’ twin pattern which is characteristic of the crystallographic orientation of the specimen and the type of stress applied. A theory of piezocrescence is proposed which depends on the principle that, at any part of a quartz specimen undergoing treatment, the crystallographic orientation developed is that which stores the maximum elastic energy. This leads to the formulation of a twin elastic function which is proportional to the difference between the elastic energies at constant stress of the two parts of the twin. Thus, if under a given system of stresses the elastic energy per unit volume in the twinned orientation is greater than in the parent orientation, then the twinned orientation is taken up by the crystal; otherwise the parent orientation remains unchanged. A knowledge of the principal stresses in a given specimen and the appropriate twin elastic function enable the ‘ideal’ twin pattern at each part of the crystal to be predicted. In the majority of the experiments there is agreement between the predicted and experimentally observed twin patterns, and the essential features of the maximum elastic energy theory would seem to be justified. The detailed testing of the theory has been handicapped by the difficulty of evaluating the principal stresses at any point within the crystal from the externally applied stress for an anisotropic body such as quartz, and also by the absence of any quantitative measure of piezocrescence other than the occurrence or absence of a twinned region. A further difficulty arises from the presence in some of the specimens of structural anomalies which hinder piezocrescence, and in this respect the study of the phenomenon is partly a study of crystal perfection.