Thermodynamic investigation of liquid Ga-As and In-As systems by the use of a drop-calorimeter

Heat contents of the Ga-As and In-As systems were measured by a drop-calorimeter in the concentration ranges of N_As=0.05 to 0.05 (GaAs, InAs) and in the respective temperature ranges of 800 t 1550 K and 700 to 1500 K. The corresponding results are illustrated in (H_TH_298.15)-temperature-composition ternary diagrams. The activities and heats and entropies of mixing were determined at temperature above 1200 K. The activities of Ga and In in both liquid systems showed a large negative deviation from Raoult's law at the compound side and a slight positive deviation in the Ga-rich and In-rich regions. Those of As showed a large negative deviation from Raoult's law. Based on the obtained thermodynamic data, partial pressure-temperature-composition correlation diagrams were constructed. Total pressure of arsenic gas species and partial pressure of As, showed a drastic increase with increasing temperature and arsenic concentration.