Melting and decomposition of orthorhombic B6Si under high pressure

TL;DR

This study investigates the melting behavior and decomposition of orthorhombic B6Si under high pressure, revealing congruent melting, a negative melting slope, and pressure-dependent disproportionation into silicon and boron-rich silicides.

Contribution

It provides the first detailed high-pressure melting curve and decomposition characteristics of B6Si, highlighting its negative melting slope and instability at high temperatures.

Findings

B6Si melts congruently between 2.6-7.7 GPa.

The melting curve has a negative slope of -31 K/GPa.

Disproportionation occurs at high temperatures with a negative slope of -92 K/GPa.

Abstract

Melting of orthorhombic boron silicide B6Si has been studied at pressures up to 8 GPa using in situ electrical resistivity measurements and quenching. It has been found that in the 2.6-7.7 GPa range B6Si melts congruently, and the melting curve exhibits negative slope of -31(2) K/GPa that points to a higher density of the melt as compared to the solid phase. At very high temperatures B6Si melt appears to be unstable and undergoes disproportionation into silicon and boron-rich silicides. The onset temperature of disproportionation strongly depends on pressure, and the corresponding low-temperature boundary exhibits negative slope of -92(3) K/GPa which is indicative of significant volume decrease in the course of B6Si melt decomposition.