The redistribution of ionic species in LiNbO3 (LN) single crystals was analyzed under an abrupt change in the growth velocity in the presence of an interface electric field during growth using the micro-pulling-down technique. The unity value of the equilibrium partitioning coefficient, k0, for the true congruent LN, cs-MgO:LN, was modified by the interface electric field and converted to kE0 (≠1). This non-unity kE0 resulted in compositional variation in the crystal during non-steady-state growth. When a certain electric current was applied to the solid–liquid interface to counterbalance the Seebeck-effect-driven electric field to make kE0 = 1 for every ionic species, no change in solute concentration was found to have occurred during non-steady-state growth. These results demonstrated that the true congruent LN crystal maintained compositional uniformity irrespective of the growth conditions. We also investigated the effect of the velocity dependence of supercooling on the Seebeck-effect-induced potential at the interface.
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