Subsolidus phase relationships of the BaO-R_2O_3-CuO_Z (R=Gd and Er) systems under carbonate-free conditions at rho O_2 = 100 Pa and r = 810 deg C

摘要

The phase diagrams of the BaO-Gd_2O_3-CuO_z and BaO-Er_2O_3-CuO_z systems were determined at 100 Pa (0.1 percent O_2 by volume, 810 deg C) by using special apparatus and a procedure for preparing carbonate-free precursors based on BaO. The diagram of the BaO-Er_2O_3-CuO_z system was confirmed to be similar to that of the Y-analog. The diagram of the BaO-Gd_2O_3-CuO_z system exhibits different features as compared to the Er-analog. While the Er-system includes the Er_2Cu_2O_5 phase, the Gd-system involves the Gd_2CuO_4 phase instead. The absence of the Ba_3R_4O_9 phase in the Gd-system affects the tie-line relations in the region bounded by BaO, BaGd_2O_4, BaGd_2CuO_5 and BagGdCu_3O_Z. In general, both the diagrams of the BaO-Er_2O_3-CuO_z and of the BaO-Gd_2O_3-CuO_z systems prepared under carbonate-free conditions are different from those obtained using BaCO_3-derived starting materials. For applications of phase equilibria to coated conductor processing, phase diagrams constructed under carbonate-free conditions should be employed.