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Acoustic investigations on intermetallics

Devraj Singh, D.K.Pandey

Acoustic attenuation due to phonon-phonon interaction and thermoelastic loss are studied in lanthanumchalcogenides along <111> crystallographic direction as a function of temperature. The second- and third-order elastic constants (SOEC & TOEC) of the materials are also calculated for the evaluation of ultrasonic coefficients. Shear wave attenuation is more than longitudinal wave attenuation for all three substances and total attenuation increases with temperature and predominantly affected with temperature variation of internal energy of thesematerials. Thermoelastic attenuation is very small as compared to phonon-viscosity loss (Akhieser loss). The behaviour of temperature dependent attenuation of these intermetallics has been discussed co-relating the important properties of metals and other NaCl-type structured crystals.