The role of hydration and complexing in the mechanism of impurity influence on crystal growth

Abstract

The influence of impurities of chlorides and nitrates of divalent Ca 2+ and Ba 2+ cations on the kinetic growth of potassium dihydrophosphate KH 2 PO 4 crystals at a saturation temperature of 323 K and rel ative supersaturation of 0.03 has been investigated experimentally. It is established that the impurity acts dif ferently, depending on the face index, the impurity concentration, cation hydration, and the stability of the complexes formed in the solution by impurity salt ions. A model is proposed to explain the different influence of impurity ions on the growth of crystal faces. This influence is determined by the different hydration of cat ions and enhanced association of cations and anions of impurity salts in the surface layer with a lower dielec tric constant.