The thermodynamics and kinetics of point defects in metal-deficient samples were studied by using Rosenburg’s 2-stage kinetic method. Sulphidation-rate measurements were carried out by using a new microthermogravimetric apparatus which permitted mass changes in the sulphidized sample to be determined, as a function of time, with an accuracy of the order of 10-7g. In one series of 2-stage kinetic experiments, the concentration of cation vacancies and their mobility were determined at 1073 to 1273K, for S activities of 10-1 to 104Pa. In agreement with published data, it was found that the cation vacancies were doubly-ionized and their concentration was a function of the equilibrium S pressure and temperature. The chemical diffusion coefficient was, in turn, found to be independent of pressure and could be described by:

D (cm2/s) = 3.88 x 10-2 exp[-81.5(kJ/mol)/RT]

This furnished an expression for vacancy migration:

D (cm2/s) = 1.29 x 10-2 exp[-81.5(kJ/mol)/RT]

By using these data, the self-diffusivity of Mn was calculated as a function of temperature and S activity:

D (cm2/s) = 6.98 x 10-4 exp[-123.5(kJ/mol)/RT] PS1/6

where PS was the S pressure.

Oxidation Kinetic Method in Studying the Defect Structure and Transport Properties of Non-Stoichiometric Manganous Sulphide. Z.Grzesik, S.Mrowec: Journal of the Physics and Chemistry of Solids, 2001, 62[11], 1967-76