Non-contacting determination of the piezoelectric coefficient <i>d</i> ₃₃ of lithium tantalate from room temperature up to 400 °C

Abstract. In this study, a non-contact, optical methodology based on laser-Doppler vibrometry (LDV) is presented to directly determine the piezoelectric constant d33 of LiTaO3 in a temperature range from room temperature to 400 °C as a proof of concept for high-temperature piezoelectric characterization. LiTaO3 is chosen as a model material as it is a representative piezoelectric material with applications in sensors and surface acoustic wave devices; however, reliable high-temperature data for d33 are only available to a limited extent, and even room temperature data, often derived from indirect or contact-based methods, show large variations. The presented approach employs freely vibrating LiTaO3 disks mounted in a minimal-contact holder, enabling off-resonant and resonant LDV measurements with temperature control in a furnace. The measured displacements, together with the applied excitation and the measured resonance behavior, yield d33 values in the off-resonant regime that range between approximately 12 and 15 pm V−1 at 21 up to 400 °C, with indications of a slight temperature dependence that remains within experimental uncertainty. The LDV technique demonstrated here provides (i) non-contact measurement virtually free of clamping effects, (ii) access to high-temperature operation limited only by the furnace, (iii) the ability to map surface distribution, and (iv) the detection of resonances, thereby enabling off-resonant frequency ranges to be determined and to compare with literature values obtained by indirect or contact methods. While this study focuses on LiTaO3, the method is applicable to systems that exhibit displacements down to a few picometers.