Journal of Pure and Applied Ultrasonics

R. K. Singh ¹, K. K. Pandey ²

Affiliations
1 Department of Physics, Banaras Hindu University, Varanasi - 221 005, IN
2 Department of Physics, H.C.P.G. College, Varanasi - 221 001, IN

Abstract

Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss has been studied from 50K to 600K in (KBr)_x (NaBr)_1-x mixed crystalline system. Starting from nearest-neighbour distance and repulsive parameters as input data, elastic constant data have been obtained at different temperatures. These values have been utilized to evaluate Gruneisen parameters, non-linearity coupling constants and sound attenuation due to phonon-phonon (p-p) interaction and thermoelastic loss, along <100> crystallographic direction of propagation for longitudinal and Shear waves. Dislocation damping due to screw and edge dislocations has also been studied. Temperature variation of (α/f²) has been found similar to dielectric crystals. Results have been discussed.

Keywords

Acoustical Dissipation, Phonon-Phonon Interaction, Elastic Constants, Relaxation Time.

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R. K. Singh ¹

Affiliations
1 Department of Physics, Banaras Hindu University, Varanasi-221005, IN

Abstract

Ultrasonic attenuation due to electron-phonon interaction and phonon-phonon interaction has been studied in alkaline-earth metals from 4.2 K to 400 K for longitudinal and shear waves. Phonon-viscosity has also been evaluated due to screw and edge dislocations. It has been found that in these metals electron-phonon interaction is the principal cause of the attenuation of the ultrasonic waves at low temperatures while phonon-phonon interaction is the dominant cause of the ultrasonic attenuation at higher temperatures i.e. 50 K and above. PACS Number : 62.20 DC, 62.65+K.

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