CRYSTAL-GROWTH AND CHARACTERIZATION OF HEAVILY MGO-DOPED LINBO3

Single crystals of LiNbO3 doped with up to 25 mol % of MgO were successfully grown. No precipitates were discovered. In studies of the change of the Curie temperatures and Raman spectra with composition, an abrupt change was observed near the composition of 10 mol % of MgO. From the model of Gallagher relating T(c) and cation vacancies and the cation occupation calculated by x-ray data, it is proposed that the Mg atoms replace the Nb atoms at Li sites. When the Nb atoms are exhausted, the Mg atoms replace the Li sites and Li vacancies are created. The amount of Mg in the LiNbO3 structure could be predicted better from the 151 cm-1 peak shift in Raman spectra than from T(c).