INFLUENCE OF IMPURITIES ON THE GROWTH KINETIC OF KDP

Growth kinetic of prismatic faces of KDP crystals in impure solutions were measured and analyzed. Two dimensional (2D) heterogeneous nucleation mechanism of growth was found to dominate at higher supersaturations, where the surface coverage of ad-molecules θ ~10-6 is about of the same order of magnitude as impurity concentration in solution. At smaller supersaturations the dislocation mechanism of growth is severely retarded by the stopper action of impurities. At the limit of the “dead ” growth zone, the much higher critical coverage θ * ~10-3 suggest the segregation coefficient of impurities increases dramatically at lower supersaturations. The influence of solution pH was discussed and the lower limit of adsorption energy of impurities (15 ÷ 18) kcal/mol was estimated