Development of Hysteresis-Free High-Precision Piezoelectric Actuators Using High Curie-Point Crystals.

由于压电陶瓷驱动器具有迟滞和蠕变特性，不适合用于精确的位置控制。本研究项目的目的是利用居里温度高达1160ﾟC的LiNbO_3晶体研制高精度的无滞回压电致动器。本课题的主要研究成果如下：1.计算了LiNbO_3晶体不同取向的压电常数，并寻找了最佳切削量。140ﾟ旋转Y切板的最大横向压电应变常数为30.3pC/N，耦合系数k23为0.51。28ﾟ旋转Y形杆的最大纵向压电应变常数为39.6pC/N，耦合系数k_&lt；22&gt；为0.6.2。研究了在居里温度以下热处理形成铁电反型层的LiNbO_3板可用作弯曲致动器，研究了反型层厚度与热处理条件的关系。结果表明，足够长的热处理时间会产生相当于板厚一半的反相层。3.用140ﾟ旋转Y形切割器制作的弯曲驱动器具有良好的线性度、无磁滞和无蠕变。4.研究了多层纵模致动器的各种制作方法。结果表明，即使是用胶粘剂叠层制作的驱动器，也没有磁滞现象，蠕变小，正负高压下都没有一定的饱和，具有良好的线性度。5.研究了压电常数随温度的变化规律。结果表明，与陶瓷驱动器相比，LiNbO_3驱动器的变化量小得多，并且可以在很宽的温度范围内工作。因此，本研究开发的LiNbO_3驱动器最适合于需要精确位置控制的应用。

Piezoelectric ceramic actuators are not suitable for precise position control, because they exhibit hysteresis and creep. The purpose of this research project is to develop hysteresis-free high-precision piezoelectric actuators using LiNbO_3 crystals with a very high Curie temperature of 1160ﾟC. The results obtained in this project can be summarized as follows: 1. The piezoelectric constants have been calculated for various orientations of LiNbO_3 and the optimum cuts have been searched. The 140ﾟ rotated Y-cut plate has a maximum transverse piezoelectric strain constant d_<23> of 30.3 pC/N and a very high coupling factor k23 of 0.51. The 28ﾟ rotated Y-bar has a maximum longitudinal piezoelectric strain constant d_<22> of 39.6 pC/N and a coupling factor k_<22> of 0.6.2. A LiNbO_3 plate with a ferroelectric inversion layer formed by heat treatment just below the Curie temperature can serve as a bending actuator The dependence of the inversion layer thickness on the heat treatment conditions has been studied. It has been shown that a sufficiently long heat treatment causes an inversion layer as thick as one-half of the plate thickness. 3. The bending actuators fabricated using 140ﾟ rotated Y-cuts have been demonstrated to exhibit excellent linearity, no hysteresis, and no creep. 4. Various fabrication methods for Multi-layer longitudinal-mode actuators have been studied. It proves that even actuators fabricated by lamination using adhesives have no hysteresis, little creep, and excellent linearity with no definite saturation for both positive and negative high voltages. 5. The temperature dependence of the piezoelectric strain constant has been examined. It has been demonstrated that the variation of d_<23> is much smaller than that of ceramic actuators and the actuators can operate over a very wide temperature range.In conclusion, the LiNbO_3 actuators developed in this research are most suitable for applications requiring precise position control.