Abstract
Internal friction of langasite is necessary for optimal performance of acoustic resonators for high-temperature sensing applications, but it remains unknown over 500℃. In this report, internal friction Q^<-1> of langasite is measured from room temperature to about 900℃ by the antenna transmission acoustic resonance (ATAR) method, which we developed inimitably. ATAR method is free from electrodes or transducers, and can measure acoustic properties at elevated temperature over 900℃. Q^<-1> of langasite is caused by the phonon-phonon interactions, point-defect relaxations, piezoelectric/carrier relaxation, and so on, and it can be written by Q^<-1> = (Δ_i / T)(ωτ_i/1+Tω^2τ_i^2) with the relaxation time τ_i of individual mechanisms. With our measurement, we found out a new relaxation mechanism around 800℃ with the activation energy of 0.49eV.
