Effect of crystal composition and growth rate on sector zoning in solid solutions grown from aqueous solutions

摘要

Sector zoning in solid solutions of Tutton's salts (NH_4)_2M(SO_4)_2-6H_2O (M = Co, Ni, Zn, Mg) and nitrates of divalent metals Me(NO_3)_2 (Me = Sr, Pb, Ba) grown from low-T aqueous solutions under controlled conditions is studied. The effect of crystal composition and growth rate (supersaturation) on the intersector difference in concentrations of isomorphic components is examined experimentally and modelled theoretically based on the phenomenological approach to crystallization in a 'solid solution-aqueous solution' system. Calculations show a predominating contribution of the selective adsorption phenomena in the formation of a sector-zoned crystal with usually minor, but sometimes a major contribution of growth kinetics.