Determination of thermal conductivity coefficient of crystals with the garnet structure at high temperatures

At high temperatures, the simple expression for thermal conductivity of crystals with the garnet structure is obtained, which allows one to determine this quantity if the lattice constant or density of these crystals is known. The thermal conductivity coefficients for the garnet crystals of different compositions calculated from the obtained formula are in a good agreement with the experimentally measured values.     

Site spectroscopy of Hf doping in Hf-doped LiNbO3 crystals

By means of Raman scattering spectroscopy we determine the site location occupied by Hf ions in photorefractive damage resistant Hf-doped LiNbO₃. At room temperature the two lowest frequency phonons are related to sites B (Nb) and A (Li), and are used to directly probe the dopant ion. For the low concentration range, the Hf ions go into the sites A whereas, for high concentration, Hf ions occupy both sites A and B. Results are compared with data obtained for pure congruent and stoichiometric crystals, and the proposed mechanism of incorporation of Hf ions in the LiNbO₃ lattice explains the threshold in the behaviour of photorefractive properties.