On the supersaturation and impurity concentration dependence of segregation coefficient in crystals grown from solutions

A general expression relating effective segregation coefficient k(eff) of impurities with their concentration c(i) in solution and growth supersaturation sigma is proposed, considering surface coverage due to impurity adsorption and dependence of accumulation and depletion of solvated host molecules at kinks on supersaturation sigma. The published experimental data on the dependence of k(eff) in some fairly and sparingly soluble compounds (potassium sulphate, zinc potassium sulphate hexahydrate, potassium dihydrogen phosphate, potassium acid phthalate. ammonium oxalate monohydrate and gypsum) on c(i) and sigma are analysed from the standpoint of the model. It was found that the new expression describes the reported experimental data satisfactorily. An analysis of the published experimental data according to the proposed model also reveals that the nature of plots of k(eff) against sigma and sigma/c(i) is associated with the accumulation and depletion of solute molecules at kinks of steps on the F faces of a crystal. (C) 2000 Elsevier Science B.V. All rights reserved.