X-ray diffractometric study in anisotropy of some lattice dynamics parameters for LiNbO3 and LiTaO3

Relative intensities and shift temperature dependences of the Bragg maxima (300) and (006) of polycrystalline LiNbO3 and LiTaO3 were determined by means of X-ray diffractometry in the FeKsub(α) radiation within a range of 300-800 K. These dependences exhibit a deviation from linearity due to the anharmonicity of thermal lattice vibrations. X-ray Debye temperature values THETAsub(psub(i)) relative to the basis axes and temperature dependences of Gruneisen's tensors γsub(ij) (T) were also determined. The anisotropy of anharmonic vibrations is estimated which is determined by the character of chemical bonds in these ferroelectrics