Assisting an experimental investigation by assessment and use of a thermodynamic description for the Cd-Ge system

Certain disagreement is observed in the binary Cd-Ge system; in our opinion this is due to the fact that cadmium presents a high vapour pressure and a low temperature of vaporisation. In this case, if experiments are performe d at constant volume, variation of pressure must be taken into account with the variation of temperature. The Cd-Ge binary system was experimentally i nvestigated by differential thermal analysis (DTA), differential scanning c alorimetry (DSC), and X-ray diffractometry. As it is difficult to realise a good measurement of the pressure in a sealed ampoule of silica, we chose t o estimate the pressure by using thermodynamic data. The optimised model pa rameters for the Gibbs energy functions of the system were obtained by usin g the optimisation/calculation programs [1, 2]. The experimental results we re reproduced correctly by calculation using the thermodynamic description established in this work. In order to explain the disagreement, a calculati on of the phase diagram at different pressures has been made by using the T hermo-Calc program [3].