Thermodynamic Study of Oxygen dissolved in Tl–Te Melts utilizing a Modified Coulometric Titration Method

Abstract

Modified coulometric titration on the electrochemical cell: O in Tl–Te melts/ZrO₂(+CaO)/Air, Pt, was performed to determine the activity coefficient of oxygen, γo, in Tl–Te melts at 1073 and 1223 K as a function of solvent composition.
The γo value for molten Tl is lowered by slight addition of tellurium and then abruptly increased around N_Te=0.333. The ln γo vs composition curve exhibits a W-shape. The enthalpy and entropy values for oxygen dissolution were found to change discontinuously with composition of Tl–Te melts around N_Te=0.333. The experimental results were qualitatively interpreted in terms of a pseudobinary model. The data were also compared and discussed with values calculated using several solution models.