Activity and diffusivity of oxygen in liquid Ag‐Yb1Ba2Cu3and Tl1Ba2Ca2Cu3alloys

摘要

We have measured the activity and diffusivity of oxygen in liquid Ag‐Yb1Ba2Cu3and Tl1Ba2Ca2Cu3at 930 and 900 °C, respectively, by a modified coulometric titration method on the galvanic cell: O_ in liquid alloys/yttria stabilized zirconia/air, Pt. The standard Gibbs formation energy and the diffusivity of oxygen in liquid Ag‐Yb1Ba2Cu3alloy for 1/2O2(1 atm)→O_(1 at. ) are determined to be Dgr;G=−247.4 kJ/g atom, andD=1.52×10−4cm2/s. The oxygen solubilityCsin the Ag‐Yb1Ba2Cu3alloy is 0.0913 at. , a factor of 5.5 higher than that in Yb1Ba2Cu3alloy. The addition of Ag does not alter the growth mechanism and the oxygen diffusion controls the film growth. The growth speed is enhanced as a result of the enhanced oxygen solubility. Dgr;Gand the diffusion coefficient of oxygen in the Tl1Ba2Ca2Cu3liquid alloy are −257 kJ/g atom and 1.2×10−4cm2/s, respectively. The oxygen solubility of the Tl1Ba2Ca2Cu3alloy at 900 °C is found to be very high at ∼5.74 at. . All thermodynamic data for oxygen in the precursor alloys are consistent with each other but there is a deviation of activity coefficient with composition for the different alloys from the theoretical model.