Partial oxygen pressure and temperature effects on the oxygen content of the Y–Ba–Cu–O melts

Abstract

The oxygen content and phase transition temperatures of equilibrated samples with Y:Ba:Cu:O molar ratios of 1:2:3: n (YBa 2Cu 3O x phase) and 1:3:4: n (YBa 2Cu 3O x +BaCuO 2 phases) were determined with a differential thermal analyzer (DTA), a thermal gravimetric analyzer (TGA) and an electrochemical oxygen analyzer. These Y–Ba–Cu–O melts were studied at partial oxygen pressures that ranged from 1×10 5 to 6 Pa and at temperatures from 1200 to 1580 K. The oxygen contents of these melts were determined with hydrogen reduction and the TGA. The oxygen content 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 1:2:3: 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 YBa 3Al 2O 7.5 in the 1:3:4: n melts, are also discussed.