V (z)‎ evaluation of crystallographic orientations effects on elastic properties of sodium cobalt germanate single crystals

Abstract EN

Herein we report on the effect of anisotropy on the elastic acoustic parameters (reflection coefficients R(θ), critical angles of wave excitation, acoustic signatures V(z), spatial periods, velocities) of sodium cobalt germanate Na2CoGeO4 single crystals with six crystallographic orientations[100], [001], [010], [110], [101], and [011].

Simulations were carried out in the case of a scanning acoustic microscope at an operating frequency of 142MHz, a half opening angle of 50° and water couplant.

Interesting results were found.

Shear modes were first excited at θS ~ 26.8° on [100] direction.

However, at other propagation directions [001], [010], [110], [101], and [011] the shear mode appears at higher angles: θS ~27.1°, 31°, 33.9°, 40.5°, 43° respectively.

Propagation of acoustic waves showed a decrease of longitudinal waves velocities from 5687 m/s for [101] direction to 4471 m/s for [011] direction.

Similar behaviors were obtained with R(θ) and V(z) curves.

These variations are due to either low or high atomic occupation of different orientations.