Thermophysical properties of Si, Ge, and Si–Ge alloy melts measured under microgravity

We have investigated density, thermal expansion, and surface tension of Si, Ge, and Si–Ge alloys in the melt and undercooled state under microgravity conditions. The experiments were conducted in the TEMPUS facility on board a Zero-G aircraft. The density of the liquid alloys as a function of composition show a nonideal behavior. Thermal expansion coefficients were found to be in the order of 10−4K−1 and was highest for Si75Ge25 melt. The surface tension is lowered with the addition of 25at.% Si in Ge. The further addition of Si increases the surface tension almost linearly with composition.