Sound velocity in the molten Bi–Te alloy

• Liquid–liquid transition in liquid Bi–Te alloy has been discussed.
• Detailed sound velocity and density measurements are presented.
• Stable atomic association Bi2Te3 persists in the molten Bi–Te system.
• Transition in liquid Bi would not be expected in the accessible super-cooled region.

Sound velocity and density measurements were carried out for the Bi–Te alloy in the liquid state as a function of temperature and composition. The results have been used to deduce the molar volume, thermal expansion coefficient, and compressibility. The temperature dependences of those thermodynamic functions are more or less similar to those observed for molten metals except for Te-rich alloys around liquidus temperature. The deviations from ideal behavior for both of the molar volume and the adiabatic compressibility as a function of composition show a cusp around 60 at.% Te, which suggests the persistence of stable atomic association Bi2Te3 in the molten alloy. Liquid–liquid crossover transition in the elemental liquids in the pnictogen column of the periodic table has been discussed.