Thermodynamic study of the cerium-cadmium system.

Cadmium vapor pressures were determined over Ce-Cd samples by an isopiestic method. The measurements were carried out in the temperature range from 690 to 1080 K and over a composition range of 48-85 at% Cd. From the vapor pressures thermodynamic activities of Cd were derived for all samples at their respective sample temperatures, and partial molar enthalpies of Cd were obtained from the temperature dependence of the activities. With these partial molar enthalpies the Cd activities were converted to a common temperature of 823 K. By means of a Gibbs-Duhem integration Ce activities were calculated, using a corresponding literature value for the two-phase field (CeCd+L) as integration constant. Finally integral Gibbs energies were calculated for the composition range 48-100 at% Cd with a minimum value of -37 kJ g-atom at 823 K in the phase CeCd. Phase boundaries of the intermetallic compounds CeCd, CeCd, CeCd, and CeCd were estimated from the vapor pressure measurements and from SEM analyses.