Abstract: The frequency dependence of the attenuation of longitudinal and transverse acoustic waves along the 100 and 1 directions in single-domain and polydomain lithium tantalate crystals at room temperature has been investigated. In the frequency range 0.15–0.4 GHz, the measurements were carried out by the modified Williams-Lamb pulse interference method. At frequencies of 0.4–1.8 GHz, the studies were performed by the Bragg diffraction of light on the acoustic waves. It is shown that the quadratic dependence of the attenuation on frequency is fulfilled in single-domain LiTaO ₃ samples. Based on the results all the six independent real and imaginary components of the complex elastic tensor for LiTaO ₃ crystals have been determined. The obtained values of these components were used to determine the velocity and attenuation coefficient of acoustic waves along other directions. It is also shown, that there is an interrelationship between the orientation dependences of the velocity and attenuation of acoustic waves. A strong increase in the attenuation coefficient of acoustic waves and the violation of the quadratic dependence of the attenuation on frequency in polydomain crystals are ascertained. A resonant mechanism of the attenuation of transverse acoustic waves along the 100 axis associated with the domain microstructure of lithium tantalate crystals was discovered.

Keywords: Lithium tantalate crystals, Acoustic wave, Anisotropy of attenuation, Domain structure, Elastic constants.

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