THERMODYNAMIC PROPERTIES OF NIAS TYPE FE1+XSB

Antimony vapor pressures were determined over Fe-Sb alloys with antimo ny contents up to about 50 at.% Sb and between 1000 and 1290 K by an i sopiestic method. Activities and partial molar enthalpies of antimony were derived from them and integral Gibbs energy values were obtained by Gibbs-Duhem integration. A theoretical model based on a statistical distribution of interstitial metal atoms and metal vacancies over the ir respective lattice sites was applied to the experimental activity d ata at 1173 K. The model yielded a value of alpha = 0.007 for the intr insic defect concentration of hypothetical stoichiometric FeSb and the interaction enthalpy between interstitial iron atoms was determined t o be H-ii = -1000 J/mol.