Lithium tantalate single crystal stoichiometry

Accurate lattice parameter, hydrostatic density and Curie temperature measurements have been made on lithium tantalate single crystals grown from different melt compositions. Crystal compositions were determined by comparing crystal Curie temperatures with those determined from well reacted ceramic specimens of known composition. These measurements showed that a stoichiometric melt produces nonstoichiometric crystals and that the congruently melting composition is 49.0 mole % Li₂O. The resulting defect model for nonstoichiometric lithium tantalate is Li[1−(5−n)x]Ta(1+x)^nxe−O₃ where n≃2 and the existence region is 46.0 to 50.4 mole % Li₂O at room temperature.