Phase relations and thermodynamic property of boron in the silicon-tin melt at 1673 K

In order to optimize the removal of B during the Si refining process using a Si–Sn solvent, thermodynamic property of B in the melt is crucial. In this study, the isothermal section for the Si–Sn–B system at 1673 K was measured by the equilibration of the liquid phase with B solid solution or silicon boride. The activity coefficient of B in the Si–Sn melt at 1673 K was evaluated, which was found to be three orders of magnitude larger in the Sn-rich side than that in the Si-rich side. This result suggests the removal of B can be achieved easily from the Si–Sn melt with the larger Sn content.

► We investigated the thermodynamic properties of B in molten Sn as well as in a Si–Sn melt.
► The isothermal section for the Si–Sn–B system at 1673 K was measured.
► The Gibbs energy of formation for SiB6 was determined as −12,600 ± 400 J/mol.
► The activity coefficient of B in the Sn-rich side was three orders of magnitude larger than that in the Si-rich side.