Chemical Reaction between Tantalum and Gallium under High Pressure

Abstract

Tantalum in contact with gallium is compressed up to 7 GPa and heated. When the temperature keeps above 50^°C of the melting temperature of gallium, the lattice constant of tantalum is approximately constant. The lattice expansion begins to increase with raising the temperature from above 300^°C. The expansion becomes about 0.28% after the heat treatment at 700^°C for 1 h. It shows the formation of a terminal solid solution phase on the tantalum side of the binary Ta–Ga phase diagram. On the other hand, a solid solution phase on the gallium side is not confirmed. The intermediate Ga₃Ta phase appears with the heating at 300^°C. The formation of the compound becomes notable after the heat treatments at 600^°C and 700^°C. The chemical reaction between tantalum and gallium is quite small up to 500^°C at 7 GPa. This shows that tantalum is stable against gallium about 400^°C over the melting temperature of gallium at the pressure. The property is useful for application as an inactive material against Ga-alloys under high pressure.