Thermodynamic study of molten Si-Ti binary alloys

The thermodynamic properties of the Si-Ti system were studied by the Langmuir effusion method for alloys containing 0 to approximately 58.7 mass%Ti. Molten samples were held in a water-cooled copper crucible and heated by power from an electron beam inside a vacuum chamber. Weight changes before and after the evaporation were measured to calculate the rate of evaporation. Evaporating species were also monitored by a mass spectrometer. The vapor pressure of titanium was much lower than that of silicon in the molar composition range of this study. The vapor pressure of silicon was calculated using the Knudsen-Hertz equation. The thermodynamic properties of titanium were calculated by the Gibbs-Duhem equation and integral excess free energy of the Si-Ti system in the above composition range and between 1873-1948 K were estimated.