Abstract
This paper focuses on identifying temperature-compensated Y-cuts (using a Cartesian coordinate system) in a piezoelectric α-GeO2 single crystal, which is isostructural–quartz α-SiO2. The study aims to minimize the frequency drift of the thickness shear mode by analyzing the resonant frequency’s first- and second-order temperature coefficients Tf(1) and Tf(2). To obtain these, the first-order, TCij(1), and second-order, TCij(2), temperature coefficients of the elastic constant, Cij, previously obtained from room temperature up to 900 °C, were calculated. Upon heating, the thermal behavior of the elastic constants indicated that some, such as C11 and C33, are stable over a range of temperatures, while others, such as C44 and C66, increase with the temperature. This paper also explores a family of singly and doubly rotated Y-cuts of α-GeO2, revealing cuts with a potential application for temperature compensation and/or linear dependence over the temperature range. The results are compared with those of the well-known piezoelectric isomorph material α-SiO2. The findings highlight that α-GeO2 is a promising material for piezoelectric devices in high-temperature environments, outperforming α-SiO2 (α-quartz), which is limited by a solid–solid phase transition at 573 °C.