Frequency and spatial dispersion of attenuation of acoustic waves in lanthanum gallosilicate crystals

The main material for piezoelectric transducers and frequency stabilizers are thermally stable quartz crystals.They can be competed with by lanthanum gallosilicate crystals (La 3 G 5 SiO 14 ), which have an electromechanical coupling coefficient 3-4 times higher and exhibit higher temperature stability of piezoelectric characteristics [1].One of the parameters limiting the use of these crystals is the acoustic attenuation.This coefficient, under the condition ωτ<<1 (ω is the circular frequency of the acoustic wave, τ is the relaxation time of thermal phonons), is determined mainly by the Akhiezer mechanism [2].In this case, the acoustic attenuation coefficient can be calculated using the complex elasticity tensor, the imaginary part of which describes the energy loss of the acoustic wave [2].La 3 G 5 SiO 14 samples were shaped as rectangular prisms, oriented along the [100] and [001] axes with an error of no more than 1 0 .Acoustic waves were excited by X-cut lithium niobate transducers.The attenuation of acoustic waves was determined by the Bragg diffraction method [2].A helium-neon laser (λ 0 = 632.8nm) was used as a light source.The accuracy of determining the attenuation coefficient was ~ 5%.The dependences of the acoustic attenuation coefficient on frequency are shown in Figure 1.It is evident that these dependences well follow the quadratic law, according to the Akhiezer mechanism.