Scanning Microscopy


The crystallization of calcium sulfate dihydrate (gypsum) and strontium sulfate (celestite) induced by the presence of barium sulfate (barite) surfaces has been studied using a Constant Composition kinetic method. In contrast to calcium sulfate, strontium sulfate appears to grow epitaxially on barium sulfate surfaces. However, barium sulfate induces calcium sulfate dihydrate precipitation from meta stable supersaturated solutions of the salt. Following nucleation, the rate of growth of strontium sulfate was found to be a second order with respect to supersaturation indicating a surface dislocation growth mechanism. The observed epitaxial growth is in agreement with calculations based on crystal lattice mismatch.

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