Measurement of Elastic Parameters of Lithium Hydroxylammonium Sulphate Single Crystal, by Ultrasonic Pulse Echo Overlap Technique

摘要

Ultrasonics is the most established and precise technique to determine the elastic parameters of materials. Elastic constants are important parameters of a crystal which provide valuable infor-mation about the bonding characteristic between adjacent atomic planes and the anisotropic cha-racter of the bonding and structural ability. Second order elastic constants can be measured by measuring the velocity of the ultrasonic pulses of different polarization along different symmetry directions. Elastic Constants of Lithium Hydroxylammonium Sulphate [LHAS] single crystal by ul-trasonic Pulse Echo Overlap [PEO] technique are reported for the first time. Large single crystals of LHAS of size [26×26×10] ?mm3 have been grown from supersaturated aqueous solution of the salt by slow evaporation technique over a period of 40 - 45 days at 305 K. Absolute velocities at room temperature (303 K) have been measured for the selected direction and modes with McSkimin criterion. The anisotropy in the elastic properties of LHAS is well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions. The elastic stiffness constants C11, C33, C44, C55, and C66, and Acoustic impedance constants and Rao’s constants in specified directions are evaluated.