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

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;
Pt, Re, Ga, Ga₂O₃/ZrO₂(+CaO)/Fe, Fe_xO, Pt
Pt, Re, (Ni–Ga), Ga₂O₃/ZrO₂(+CaO)/Fe, Fe_xO, Pt
Activities 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.