Precise Determination of Acoustical Physical Constants of LiNbO_3 and LiTaO_3 Single Crystals

本研究发展了一种测定压电晶体声学物理常数的新方法，利用线聚焦束声学显微镜和体超声光谱两种系统，精确测定了LiNbO_3和LiTaO_3单晶的所有独立常数，包括密度.为了提高两种系统的可靠性和重复性，稳定了温度测量环境，并引入了激光干涉仪测量绝对距离。绝对精度优于（]SY. ±. [）0.01%的速度已被忽略。用一个晶锭制备了许多具有光学抛光表面和良好的前后表面平行度的LiNbO_3和LiTaO_3晶面样品.提出了一种确定声物理常数的新方法，刚度，压电，和介电常数，已开发使用这两个系统的速度测量。测定了LiNbO_3和LiTaO_3的声物理常数，给出了体声速和声表面波声速的五位有效数字.首次测定了多畴LiTaO_3晶体的弹性常数，并与单畴LiTaO_3晶体的弹性常数进行了比较。结果表明，引入压电效应的极化操作是造成单畴和多畴晶体弹性性质差异的主要原因。

In this study, we have developed a new method of determining the acoustical physical constants associated with piezoelectric crystals, using two systems of line-focus-beam acoustic microscopy and bulk ultrasonic spectroscopy, and have determined precisely all the independent constants of LiNbO_3 and LiTaO_3 single crystals, including the density.1. In order to improve reliability and reproducibility of the two systems, the measurement environment of temperature has been stabilized and a laser interferometer has been introduced to measure the absolute distance. Absolute accuracy of better than (]SY.+-。[)0.01% in velocity has been achieved.2. Many crystalline plane specimens of LiNbO_3 and LiTaO_3 with optically polished surfaces and excellent parallelism of front and back surfaces have been prepared from one ingot for each crystal.3. A new method of determining the acoustical physical constants, viz., stiffness, piezoelectric, and dielectric constants, has been developed using the two systems for velocity measurements.4. The acoustical physical constants of LiNbO_3 and LiTaO_3 have been determined, which provide five significant digits for bulk and surface acoustic wave velocities.5. The elastic constants for multi-domain LiTaO_3 crystals have been also determined, for the first time, and have been compared with those for single-domain LiTaO_3 crystals. It has been shown that the poling operation to introduce piezoelectricity is responsible for the differences of elastic properties between single-and multi-domain crystals.