GROWTH-KINETICS AND MORPHOLOGY OF POTASSIUM DIHYDROGEN PHOSPHATE CRYSTAL FACES IN SOLUTIONS OF VARYING ACIDITY

Changes in the solution acidity do not influence the growth rate of bi pyramidal faces, however, within the limits of 20% it can be changed b y uncontrollable impurities existing in the solution. For steps on pri smatic faces in acid and alkali solutions a decrease of the critical s upersaturation sigma, at which a sharp increase of the velocity occur s, is observed. This is indicative of the decrease of the surface conc entration of the adsorbed impurity, which retards the growth. The more the solution composition deviates from the stoichiometric one, the mo re does the value of sigma diminish. It is shown that pH does not aff ect the free surface energy of end faces of steps and their kinetic co efficients. The values of kinetic coefficients of steps of different o rientation on prismatic and pyramidal faces are determined. The featur es of the macrosteps formation with the supersaturation increase are d escribed in solutions of varying acidity. The effect of pH on the crys tal habit is discussed.