The elastic stiffness of langasite at high temperatures and its temperature compensated orientations

Abstract

The langasite crystal has the capability of no phase change at temperatures exceeding 600°C for high temperature applications. Since the material properties of langasite were measured usually at 25 0C as the reference temperature they are no longer accurate at high temperature environments. We employ a Lagrangian formulation to investigate the temperature behavior of thickness vibrations of langasite in a wide temperature range from 25°C to 600°C. The analysis only requires the elastic constants and their effective temperature derivatives of elastic constants and thermal expansion coefficients to predict the material constants at any given temperature. Based on the new values of the elastic constants and thermal expansion coefficients, the zero-valued temperature coefficients of frequency are investigated. The presently identified temperature compensated crystal cuts of the thickness-shear modes of langasite at different temperatures were compared with those at reference temperature and also with some cuts found in the literature.