Phase diagram for 1/2 Yb2O3-BaO-CuO

The phase diagram of the 1/2 Yb2O3-BaO-CuO system has been studied in oxygen at 935 degrees C. An inert gas glove box was used for sample manipulation and storage to avoid problems caused by reactions of BaO-rich samples with atmospheric CO2 and H2O. Ternary phases prepared and identified were YbBa2Cu3Ox (Yb-123), YbBa4Cu3Oy (Yb-143), YbBa6Cu3Oz (Yb-163), and Yb2BaCuO5 (Yb-211). Compositions on and around the tie line between Yb-211 and BaCuO2 were also prepared and studied. X-ray diffraction measurements and differential thermal analyses were carried out to identify phases present. Results indicated that the 1/2 Yb2O3-BaO-CuO system is very similar to the 1/2 Y2O3-BaO-CuO system with the same ternary phases and with no extensive solid solution. The Yb-123 phase is the only superconducting phase in the system with an observed T-c of 90 +/- 1 K. The Yb-163 phase was observed to react rapidly with ambient air. (C) 1997 Elsevier Science B.V.