Temperature characteristics of acoustic modes in SiO2, LiNbO3, LiTaO3, Bi12GeO20, and Bi12Si20 piezoelectric crystal plates

Abstract

Temperature coefficients of delay of zero- and higher-order acoustic plate modes in the most widespread piezoelectric crystals are calculated and measured. It is shown that, along with the well-known dependence of these coefficients on material constants (typical of surface and bulk acoustic waves), their values for plate modes depend also on the mode number, plate thickness, acoustic wavelength, and thermal expansion coefficient of the crystal across the plate thickness, which allows one to change the temperature sensitivity of plate modes in wide limits without changing the material and orientation of the crystal. For some combinations of the aforementioned parameters, very small temperature changes Δt ~ 10^–3°C are detected.