Thermally induced beam distortions in laser ceramics with arbitrary grain size have been investigated. A model for the spatial spectral density of dielectric permeability variations was suggested. The average scattered intensity was carried out using the small disturbances method. The directional pattern of the scattered field and the extinction coefficient have been obtained. The scattered power and the depolarization ratio fit with the corresponding values obtained in the geometrical optics approximation in the range of its validity.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.