A thermodynamic study of the cadmium-neodymium system

Cd vapor pressures were determined over Cd-Nd samples by an isopiestic method. The measurements were carried out in the temperature range from about 690 to 1200 K and over a composition range between 48 and 92 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 873 K. By means of a Gibbs-Duhem integration Nd activities and integral Gibbs energies were calculated, using a literature value of Δ_fG for the phase Cd₆Nd as integration constant. A minimum of Δ_fG ≈ -38 kJ g-atom^-1 at 873 K was obtained for the phase CdNd, a value that compares well with other CdRE compounds.