Thermodynamic Study of Solid Ni-Ga Alloys by E.M.F. Measurements Using Solid Electrolyte Cells

Abstract

E.M.F. of a galvanic cell with the solid electrolyte (ZrO₂+CaO) was measured to determine the activities of gallium in the temperature range of 800∼1000°C and the composition range of 5∼58 at%Ga for solid Ni-Ga alloys, and thermodynamic functions were derived from the results. The cells used were as follows:
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Activites of both components showed large negative deviations from Raoult’s law; Activity changes with composition in nickel-rich α-solid solution and in the α′(Ni₃Ga)-phase were small, but very large in the β(NiGa)-phase. Relative integral molar free energies of formation showed minimum values at the stoichiometric composition NiGa. Intergral enthalpies and entropies of formation showed relatively large negative values.