Temperature dependance of acoustic wave attenuation in dielectric rubidium halide crystals.

Acoustic attenuations coefficients divided by frequency square (α /f2) have been computed for both longitudinal and shear waves propagating along the (100) axis and polarised along (110) direction in the Rubidium halide crystals (RbCl, RbBr and RbI), which are dielectric in nature. These attenuation coefficients are determined for a wide range of temperature between 100 – 400 K. Initially, Second order and Third order elastic constants (SOEC and TOEC) of these dielectric crystals were determined by using the Brugger's definitions for elastic constants and using these the Gruneisen parameters γ i j and 〈 γ i j 〉 were found out. Temperature dependent non-linearity parameter DL and DS, for the longitudinal and shear waves were determined with the help of Gruneisen parameters. The computed attenuation coefficients for the Rubidium halide dielectric crystal are found to be temperature dependent. Attenuation of high frequency acoustic waves is found to have maximum value for RbI crystal and minimum value for RbCl crystal, while, for RbBr crystal it is intermediate between the above two values. Phonon-Phonon interaction is the most prominent cause of the acoustic attenuation of the high frequency waves propagating through the crystals. Longitudinal waves are more attenuated as compared to shear waves. [ABSTRACT FROM AUTHOR]