Experimental Fusion Curves of Indium and Tin to 105 000 Atmospheres

Abstract

The experimental fusion curves of indium and tin have been determined to a pressure of 105 000 atmospheres. The melting point was detected at various pressures by means of a sharp increase in the electrical resistance of the sample, which gave rise to a sudden increase in the sample temperature. The melting temperature of indium was found to rise smoothly from a normal value of 156\ifmmode^\circ\else\textdegree\fi{}C to a value of 417\ifmmode^\circ\else\textdegree\fi{}C at 105 000 atm. The experimental data are fitted very well by the Simon equation $\frac{P}{a}={(\frac{T}{{T}_{0}})}^{c}\ensuremath{-}1$, with $a=15000$ atm, $c=4.34$, and ${T}_{0}=429\ifmmode^\circ\else\textdegree\fi{}$K. No evidence of polymorphism is observed. A phase transition is found for tin, with a triple point on the fusion curve at 38 000 atm, 318\ifmmode^\circ\else\textdegree\fi{}C. The melting temperature for the first phase rises smoothly from its normal value of 232\ifmmode^\circ\else\textdegree\fi{}C to the triple point, and the data are fitted very well by the Simon equation with $a=7400$ atm, $c=11.3$, ${T}_{0}=505\ifmmode^\circ\else\textdegree\fi{}$K. The melting temperature for the second phase rises smoothly from the triple point to a value of 500\ifmmode^\circ\else\textdegree\fi{}C at 105 000 atm, and the data are fitted very well by the Simon-type equation $\frac{(P\ensuremath{-}38000)}{21800}={(\frac{T}{591})}^{5.25}\ensuremath{-}1$. The uncertainty is estimated to be approximately \ifmmode\pm\else\textpm\fi{}5% in the measured melting temperature, \ifmmode\pm\else\textpm\fi{}5% in the pressure calibration, \ifmmode\pm\else\textpm\fi{}20% in the Simon coefficient $a$, and \ifmmode\pm\else\textpm\fi{}2% in the Simon exponent $c$.