Partitioning of ionic species and crystallization electromotive force during the melt growth of LiNbO3 and Li2B4O7

The dependence of the crystallization electromotive force (EMF) on the Li2O composition of the melt in the growth of LiNbO3 (LN) and Li2B4O7 (LB4) crystals was measured using a micro-pulling-down (μ-PD) method. The crystallization EMF developed during the growth of LN crystals continuously decreased with increase in Li2O composition. The eutectic compositions in the Li2O–Nb2O5 system were found to be peculiar compositions, at which the development of the crystallization EMF was prevented owing to no degree of freedom in the Gibbs phase rule. It was found that no segregation of the ionic species occurred in the LB4 growth from the melt with the stoichiometric composition, which suggested that the equilibrium partitioning coefficients for all the chemical species in the stoichiometric LB4 melt were unity.