Phase transitions of a simple hexagonalIn0.2Sn0.8alloy under high pressure

Abstract

Phase transitions of a Sn-In (20 at. % In) alloy have been studied under pressures up to 30 GPa in diamond anvil cells by energy dispersive and angle dispersive x-ray diffraction. The simple hexagonal low-pressure phase $(\mathrm{hP}1)$ was found to transform at pressures above 13 GPa to a mixture of two phases: body-centered tetragonal $(\mathrm{tI}2)$ and close-packed hexagonal $(\mathrm{hP}2).$ This transformation of the ${\mathrm{In}}_{0.2}{\mathrm{Sn}}_{0.8}$ alloy under pressure is considered as a decomposition of the low-pressure phase into a mixture of two phases, whereby the $\mathrm{hP}2$ phase begins to dominate with the further increase of pressure. Above 23 GPa only the $\mathrm{hP}2$ phase was observed. The axial ratios for all three phases in ${\mathrm{In}}_{0.2}{\mathrm{Sn}}_{0.8}$ and their variations on compression are discussed.