High-pressure–high-temperature phase diagram of tin

The high-pressure--high-temperature behavior of tin has been measured with x-ray diffraction and laser-heated diamond anvil cells up to 225 GPa at 300 K and to 110 GPa and $\ensuremath{\sim}4000$ K. Temperature has been measured using conventional point pyrometry as well as a four-color mapping pyrometer. The stability fields of Sn liquid and solid phases $(\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Sn}, \mathrm{bct} \ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{Sn}, \mathrm{bcc}\text{\ensuremath{-}}\mathrm{Sn}, \mathrm{hcp}\text{\ensuremath{-}}\mathrm{Sn})$ have been constrained. The high-pressure hcp-Sn phase has been observed but at higher pressure than under hydrostatic compression. The bcc-bct transition conditions are measured, up to a bcc-bct-liquid triple point at 18.9 GPa/1410 K. A lower bound for bcc-Sn melting line is proposed (Simon equation): ${T}_{m}=581{((P\ensuremath{-}2.86)/6.44+1)}^{0.71}$ ($P$ in GPa, ${T}_{m}$ in Kelvin).