Activity measurement of liquid Te-In alloys by an EMF method using a zirconia electrolyte

The activity of the liquid Te-In system has been determined by the emf measurement of the following galvanic cell: ⊕Pt/Ni(s), NiO(s) |ZrO₂(+CaO) |Te-In(1), In₂O₃(s) /Re/Pt$DMIN (for N_In=0.18-0.90 at 923-1116 K). The activity of indium in liquid Te-In alloys at 1000 K and 1050 K shows large negative deviations from Raoult's law in the tellurium-rich region and remarkable negative to positive deviations from ideality in the indium-rich region. The activity of tellurium at the same temperatures exhibits negative deviations from Raoult's law over the whole concentration range. The α functions of indium in the alloys show curves against N_In, suggesting the absence of the behavior of a regular solution. The free energy of mixing at 1050 K has large negative values compared with ΔG^id, and the peak value of ΔG shows -27.0 kJ/mol at about N_In=0.55. Heat of mixing shows very large negative values. The peak value of ΔH is -20.6 kJ/mol at about N_In=0.49.