Incorporation of hexavalent impurities into LiNbO3

The influence of the valence state on the lattice location of impurities in lithium niobate LiNbO3 crystals was investigated using hexavalent dopants (W6+ and U6+) introduced by doping of congruent melt. The distribution coef ficients were determined by Rutherford Backscattering Spectrometry to be k = 0.2 for W and k = 0.07 for U. Channeling studies showed that the hexavale nt impurities are located on the Nb site in both cases. The preferential oc cupation of Nb sites suggests that the formation of Li-vacancies is favored . This result is a strong evidence for the Li-vacancy defect model for cong ruent LiNbO3.