Naumenko N, Solie L
Crystal Physics Department, Moscow Steel and Alloys Institute, 117936 Moscow, Russia.
IEEE Trans Ultrason Ferroelectr Freq Control. 2001 Mar;48(2):530-7. doi: 10.1109/58.911736.
The results of a theoretical and experimental investigation of the SAW propagation characteristics in an optimal region of langasite defined by the Euler angles phi from -15 degrees to +10 degrees, theta from 120 degrees to 165 degrees, and psi from 20 degrees to 45 degrees are presented. Based on temperature coefficients of the elastic constants derived from experimental data, some optimal orientations of langasite characterized by high electromechanical coupling factor (k2), zero power flow angle (PFA) and low or zero temperature coefficient of frequency (TCF) were found. The SAW velocity in the region of interest is highly anisotropic; this results in a significant amount of diffraction, which must be taken into account in the search for orientations useful for SAW devices. An orientation having simultaneously zero PFA, zero TCF, negligible diffraction, and relatively high piezoelectric coupling has been found and verified experimentally. The experimental results are in excellent agreement with the calculated SAW characteristics. The frequency response of a SAW device fabricated on the optimal cut of langasite is presented and demonstrates that high performance SAW filters can be realized on this optimal cut of langasite.
本文给出了在硅酸镧镓晶体由欧拉角φ（-15度至+10度）、θ（120度至165度）和ψ（20度至45度）定义的最佳区域内表面声波（SAW）传播特性的理论与实验研究结果。基于从实验数据得出的弹性常数温度系数，发现了一些硅酸镧镓晶体的最佳取向，其特征为机电耦合系数（k2）高、功率流角（PFA）为零以及频率温度系数（TCF）低或为零。在感兴趣的区域内SAW速度具有高度各向异性；这会导致大量衍射，在寻找对SAW器件有用的取向时必须考虑到这一点。已经找到了一个同时具有零PFA、零TCF、可忽略的衍射以及相对较高压电耦合的取向，并通过实验进行了验证。实验结果与计算得到的SAW特性非常吻合。给出了在硅酸镧镓晶体最佳切割面上制作的SAW器件的频率响应，表明在这种硅酸镧镓晶体的最佳切割面上可以实现高性能的SAW滤波器。
