Influence of impurity doping on the partitioning of intrinsic ionic species during the growth of LiNbO3 crystal from the melt

The segregation of intrinsic ionic species of LiNbO3 during crystallization generates electromotive force (EMF) at the growth interface. The EMF was measured during the growth of LiNbO3 crystal doped with MgO, ZnO, ZrO2 and MnO2 in the concentration range from 0 to 12 mol% using a micro-pulling-down growth system. The influence of these impurities on the partitioning of intrinsic ionic species of LiNbO3 was examined. In the case of MgO-, ZnO- and ZrO2-doping, crystallization EMF had a minimum value at the concentration where the impurity ion changed its partitioning site from the Li-site to the Nb-site, as confirmed by Raman scattering measurements. The crystallization EMF of MnO2-doped LiNbO3 showed no such minimum value because Mn4+ ion did not change its partitioning site. These results demonstrate that it is the segregation of the intrinsic ionic species that generates the crystallization EMF rather than that of impurities and that the partitioning behavior of intrinsic ionic species of LiNbO3 is greatly affected by the partitioning site of impurity ions.