Partial Pressure and Temperature Effects on the Oxygen Content of the Y-Ba-Cu-O Melts

Hunt R.D. , Beahm E.C. , Voronin G.F.

Physica C (in print)

The oxygen content and phase transition temperatures of equilibrated samples with Y:Ba:Cu:O molar ratios 1:2:3:n (YBa2Cu3Ox phase) and 1:3:4:n (YBa2Cu3Ox+BaCuO2 phases) were determined with a differential thermal analyser (DTA), a thermal gravimetric analyser (TGA), and an electrochemical oxygen analyser. These Y-Ba-Cu-O melts were studied at partial oxygen pressures that ranged from 0.1 to 0.00006 Mpa and at temperatures from 1200 to 1580 K. The oxygen contents of these melts were determined with hydrogen reduction and the TGA. The oxygen contents of the 1:2:3:n melts decreased as the temperature increased and as the partial oxygen pressure decreased. The same pattern for the partial oxygen pressure was observed for the oxygen content in the 1:3:4:n melts. However, at a given partial oxygen pressure, the highest oxygen content in a 1:3:4:n melt was observed at a temperature approximately 100 K above the initial melting temperature. The liquidus temperatures for 12:2:3:n and 1:3:4:n always decreased as the partial oxygen pressures decreased. Finally, the compositions of the melts, which included the formation of the YBa3Al2O7.5 in the 1:3:4:n melts, are also discussed.

Laboratory of Chemical Thermodynamics