Nonstoichiometry and Crystal Growth of Lithium Niobate

Deviations from stoichiometry occurring during the crystal growth of lithium niobate have been studied by 93Nb NMR and by shifts in the ferroelectric transition temperature. The high-temperature phase equilibria of nonstoichiometric lithium niobate were accurately determined by these techniques together with DTA and crystal-growth experiments. The congruently melting composition is located at 48.6 mole% Li2O and the solid-solution region at room temperature extends from 48% to 50% Li2O. The implications of growth at noncongruently melting compositions on the compositional uniformity of lithium niobate are discussed in detail.