LATTICE-CONSTANTS OF K-DOPED AND MG-DOPED LINBO3 - COMPARISON WITH NONSTOICHIOMETRIC LITHIUM-NIOBATE

The dependencies of lithium niobate lattice constants on stoichiometry and concentration of K and Mg dopants were investigated with the help of X-ray powder diffraction. It was found that in contrast to MgO dop ant, an addition of K2O to the congruent LiNbO3 melt leads to a decrea se of the lattice constants. A similar reduction of a and c parameters is observed if the Li content of the crystal is increased, which is a ccompanied by an improvement of the lithium niobate lattice structure because of diminishing concentration of intrinsic nonstoichiometric de fects.