THERMODYNAMIC ASPECTS OF PYRITE FILM FORMATION BY SULFUR CONVERSION OF IRON

Experimental data and thermodynamic considerations show that direct reaction of the elements can produce pure FeS2. Polycrystalline iron was converted in a sulphur atmosphere. The iron sulphide samples were characterized with scanning electron microscopy, X-ray diffractometry and small-spot electron spectroscopy for chemical analysis. Based on these results and on thermodynamic calculations employing literature data, a model for layer growth involving a complex mechanism is proposed. In a first step, FexS is formed chemoepitaxially followed by a conversion to FeS2 by a chemoendotaxial reaction with sulphur. Grain boundaries play a decisive role in the growth process.