Phase diagram of tin determined by sound velocity measurements on multi-anvil apparatus up to 5 GPa and 800 K

The tin β–γ–liquid triple point and the melting curve at high pressure have been controversial for a long time. Apart from being of fundamental importance, the sound velocity at high pressure and high temperature also provides a practical approach for determining melting curves and phase boundaries. We investigated the sound velocities and phase diagram of tin up to 5 GPa and 800 K by ultrasonic measurements on a multi-anvil apparatus. The β–γ–liquid triple point obtained in this work is 3.02 ± 0.05 GPa and 562 ± 2 K. The experimental data and the extrapolated melting curve of the γ phase using the Simon-type equation are in good agreement with the theoretical and most of the experimental results at high pressure. These results indicate that sound velocity measurements based on multi-anvil apparatus can be a convenient and reliable approach to determine the high-pressure melting curve and phase boundaries of materials.