Measurement of activity of gallium in liquid Ga-Sb-Ge alloys by EMF method with zirconia as solid electrolyte

The emf of galvanic cells with zirconia solid electrolytes was measured from 975 to 1242 K on binary Ga-Ge alloys and from 1058 to 1236 K on ternary Ga-Sb-Ge alloys by use of Ga-Ga2O3 as a reference electrode. From the emf values the activity of gallium in the liquid alloys is determined. At 1073 K the activity of gal hum in the Ga-Ge alloys and in the three pseudobinary alloys Ga-(SbyGe1-y) where y=0.25, 0.50 and 0.75 shows small negative deviations from ideality. Isoactivity curves in the ternary Ga-Sb-Ge alloys were derived by combining the activity data of Ga-Sb, Ga-Ge and the ternary alloys. The shape of the curves at 1073 K is simple in the Ga-poor region, but shows a very small wavy form with increasing Ga concentration. Isovalues curves in the excess Gibbs energies of mixing in the ternary alloys are derived from Darken's method, and the results are compared with the model calculation proposed by Chou based on the experimental data in three binary systems. The shape of isovalue curves in Delta G(xs) is similar to those obtained from Chou's method, but the agreement between them in the values is not good.