Thermodynamic investigation on the si-ge binary system by calorimetry and knudsen cell mass spectrometry

The partial enthalpy of Si in Si-Ge liquid alloys was determined by drop calorimetry at 1327 K in the 0 < Xsi< 0.03 concentration range with a high-temperature Calvet calorimeter. The excess Gibbs energy of formation of the melt was derived from Knudsen cell mass spectrometric measurements over the entire range of composition using the intensity ratio method. The thermodynamic behavior of the liquid phase of the system is regular and presents positive deviations from ideal mixing. It corresponds to the following thermodynamic functions for the melt: G^ex = 6.0XSiXGe kj/mol at 1723 K; and H^ex = 6.61XSiXGe kj/mol. The phase diagram calculated assuming such a behavior agrees well with the data of the literature. Some liquidus points obtained from the breaks existing in the logarithm of the vapor pressure versus the inverse temperature plots also agree.