Thermodynamic properties and phase equilibria in the Ca-Sb system

A Knudsen effusion technique combined with mass-spectrometric analysis of the evaporated species was used to investigate the gaseous phase and to determine the thermodynamic properties of alloys of calcium with antimony in the temperature range from 933 to 1669 K. Concentration of antimony varied from 50.2 to 63.5 mol.%. The thermodynamic properties of the liquid phase were approximated by the association solution model, assuming that four types of associates Ca3Sb2, Ca3Sb, Ca2Sb and CaSb can exist in the melt. The Gibbs energies of formation of compounds from solid components were expressed by the equations: Delta(f)G(Ca11Sb10) = -(21884442 +/- 14595) -(43.47 +/- 12.34)T, and Delta(f)G(Ca5Sb3) = -(919276 +/- 5110) +(34.24 +/- 4.75)T, J mol(-1) The obtained data were used for the computation of the part of the Ca-Sb phase diagram, corresponding to the composition range studied.