It was performed the investigation of the behavior of laser beam scattering at different conditions: within of the crystal, on the screen in far field. In dependence on direction and polarization of the laser beam the track of the beam within of crystal has the homogenous or speckle structure; on the screen in far field - rounds, ellipses or stripes forms. The changes of light scattering at heating of crystal have observed near 300°C и 560°C (structural phase transitions) and near 200°C, 240°C and 270°C (temperature of transformation of nanodomain structures)]. It was observed the changes of light scattering patterns in range of 460 – 560°C. Investigations of the temperature behavior of Raman scattering lines and central peak was performed in work of [5]. On the basis of analysis of the temperature behavior of the Raman scattering spectra, central peak, patterns of light scattering in far field above and’ below 300°C and structural investigations of [1 – 4] have been made conclusion about new incommensurate phase above 300°C.