Study of the mechanism of crystallization electromotive force during growth of congruent LiNbO3 using a micro-pulling-down method

We have investigated the crystallization electromotive force (EMF) during the growth of congruent LiNbO3 (LN) by exploiting the features of a micro-pulling-down (μ-PD) method. The electric potential distribution around the growth interface that was measured in the μ-PD system was attributed to the Seebeck effect and several mV of crystallization EMF. The mechanism of the crystallization EMF during the growth of congruent LN from the melt was explained using a model wherein segregation of the ionic species in the melt formed a net ionic charge at the growth interface resulting in the development of an EMF. Redistribution of the net ionic charge, which was analyzed on the basis of a one-dimensional differential equation that included electric-field-driven transport in the melt, well reproduced the experimental data of the nonlinear dependence of crystallization EMF on the growth rate. We concluded that the crystallization EMF occurred during crystal growth of the congruent LN owing to the ionic-charge accumulation at the growth interface.