Microthermogravimetry in studying the defect and transport phenomena in transition metal sulfides

The chemical diffusion coefficient and point defect concentration in metal-deficit sulfides (Co9-yS8, Ni1-yS and Mn1-yS) has been studied as a function of temperature and sulfur activity using reequilibration and two-stage kinetic methods. Measurements have been carried out in a novel microthermogravimetric apparatus, enabling the mass changes of the sulfidized samples to be determined as a function of time with the accuracy of the order of 10(-6) g. The diffusivity and defect concentration in investigated sulfides have been studied at high temperatures (873-1273 K) in pure sulfur vapours (10(-1)-10(4)) Pa) and H-2-H2S gas mixture with P(S-2) ranging from 10(-5) up to 1 Pa. The results described in the present paper show clearly that the microthermogravimetry may successfully be utilized in studying the defect and transport properties of nonstoichiometric metal sulfides. (C) 2002 Elsevier Science B.V. All rights reserved.