The effect of native defects upon the domain structure of Fe-doped material was investigated. Two methods were used to reduce the number of native defects. One was co-doping with Mg, and the other was the addition of K2O to the congruent melt. When grown from such melts, the samples exhibited a multi-domain nature. Co-doping with Mg changed the domain structure, although the crystals were still multi-domain. Upon adding K2O, single-domain crystals were obtained. The change in domain structure which was produced by Mg doping was attributed to compensation of the stoichiometric defects. A reduction in the number of intrinsic defects, due to a change in the Li/Nb ratio of the crystal which resulted from adding K2O to the melt, led to a mono-domain structure.

V.Bermúdez, P.S.Dutta, M.D.Serrano, E.Diéguez: Journal of Physics - Condensed Matter, 1997, 9[28], 6097-101