A model of effective segregation coefficient, accounting for convection in the solute layer at the growth interface

Abstract

A model of the effective segregation coefficient keff is obtained by using integral boundary layer analysis. The model provides a simple relation between keff and the actual physical thickness of the solute layer δD, the convective velocity in the solute boundary layer VD, the equilibrium segregation coefficient k, the growth rate R and the characteristic lenght of the growth interface L. A good agreement is obtained between the model and the data in the literature (e.g. the data used to fit the BPS model). The model provides a criterion for the maximum convective velocity, allowing diffusion-controlled segregation. The criterion indicates that diffusion-controlled segregation of solvent-solute system with k ≪ 0.1 may not be feasible even in microgravity.