Composition dependence of the lattice constants in LiTaO3

Abstract The composition range of lithium tantalate was found between 46.5 and 50.0 mole% Li. The congruent melt composition, from which homogeneous single crystals can be grown, was determined at about 48.5 mole% Li2O. Due to Li2O evaporation during the reaction of Li2CO3 and Ta2O5 the starting composition depends on the reaction conditions. The lattice constants change with the composition comparable to LiNbO3.