The thallium-indium phase diagram as a function of composition, temperature and pressure

Abstract

The thallium-rich region of the thallium-indium phase diagram was determined from atmospheric pressure to 5.5 kbars primarily from electrical resistivity data obtained as a function of composition, temperature and pressure. Corroborative X-ray diffraction data were taken at atmospheric pressure. Extrapolation of the results of this investigation to high pressures indicates that a triple point occurs between three solid allotropes of thallium at 162°C and 35.8 kbars. The high pressure phase was found to be continuous with the f.c.c. phase observed at atmospheric pressure for thallium containing 40–77 at. % indium. This result indicates that the crystal structure of the high pressure allotrope of thallium is f.c.c. The remaining two phases in equilibrium at the triple point are continuous with the h.c.p. low temperature phase and the b.c.c. high temperature phase observed for pure thallium at atmospheric pressure. A revised phase diagram for the thallium-indium system at atmospheric pressure is also proposed.