Solubility and activity of oxygen in liquid germanium and germanium-copper alloys

Abstract

The solubility of oxygen in liquid germanium in the temperature range 1233 to 1397 K, and in liquid germanium-copper alloys at 1373 K, in equilibrium with GeO₂ has been measured by the phase equilibration technique. The solubility of oxygen in pure germanium is given by the relation 6470 log(at, pct 0) =-6470/T + 4.24 (±0.07). The standard free energy of solution of oxygen in liquid germanium is calculated from the saturation solubility, and recently measured values for the free energy of formation of GeO₂, assuming that oxygen obeys Sievert's law up to the saturation limit. For the reaction, ½O₂(g)→O_Ge ΔG ° =-39,000 + 3.21 T ( ±500) ca1 = -163,200 + 13.43 T (±2100) J. where the standard state for dissolved oxygen is that which makes the value of activity equal to the concentration (in at. pct), in the limit, as concentration approaches zero. The effect of copper on the activity of oxygen dissolved in liquid germanium is found to be in good agreement with that predicted by a quasichemical model in which each oxygen was assumed to be bonded to four metal atoms and the nearest neighbor metal atoms to an oxygen atom are assumed to lose approximately half of their metallic bonds.