Ultrasonic attenuation due to phonon–phonon interaction, thermoelastic loss anddislocation damping in transition metal carbides

Abstract

Temperature dependent ultrasonic attenuation due to phonon–phonon (p–p) interaction,thermoelastic loss and dislocation damping due to screw and edge dislocations have beeninvestigated in fcc (NaCl B1 type) structured group IVb and Vb monocarbides (transitionmetal carbides, namely TiC, ZrC, HfC, VC, NbC and TaC) in the temperature range50–500 K, along the three crystallographic directions of propagation, namely [100], [110] and[111] for longitudinal and shear modes of propagation. The second- and third-order elasticmoduli (SOEM and TOEM) obtained at different temperatures using the electrostatic andBorn repulsive potentials and taking interactions up to next-nearest neighbours, have beenused to obtain Gruneisen numbers, acoustic coupling constants and their ratios alongdifferent directions of propagation and polarization for longitudinal and shear modes ofwave propagation. Temperature variation of the phonon relaxation time showsexponential decay. The results have been discussed and compared with availabledata.