Thermodynamic Study of Solid Ni–Ga Alloys by E.M.F. Measurements Using the Solid Electrolyte

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;Pt, Re, Ga, Ga2O3/ZrO2(+CaO)/Fe, FexO, PtPt, Re, (Ni–Ga), Ga2O3/ZrO2(+CaO)/Fe, FexO, PtActivities of both components showed large negative deviations from Raoult’s law; Activity change with composition in a 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. Integral enthalpies and entropies of formation showed relatively large negative values.