Iwao Katayama1, Nobumasa Kemori2 and Zensaku Kozuka1
1Department of Metallurgy, Faculty of Engineering, Osaka University, Suita
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 composition range of 0 ∼ 58.9 at%Ga for solid Co-Ga alloys, and thermodynamic functions were derived from the results. The cells used were as follows:
Pt, Re, Ga, Ga2O3/ZrO2(+CaO)/Fe, FexO, Pt
Pt, Re, Co-Ga alloy, Ga2O3/ZrO2(+CaO)/Fe, FexO, Pt.
Activities of gallium showed large negative deviations from Raoult's law in the whole composition range investigated. Activity changes with composition in cobalt rich α -solid solution were small, but very large in the β (CoGa)-phase. Activities of cobalt showed very small positive deviations from Raoult's law in the α -solid solution, but very large negative ones in the β -phase. Activities of gallium and free energies of formation showed larger values than those of Ni-Ga alloys. Larger solubilities of gallium in cobalt in the temperature range of 800 ∼ 1000°C than those shown in the phase diagram of Elliott were found. Standard free energy of formation of Ga2O3(s) was shown by
Please do not copy without permission.