Effect of oxygen partial pressure on the preparation of phase-pure YbBa2Cu3O7-y superconductor by solid-state sintering method

In preparing REBCO superconductors, the oxygen partial pressure (PO2) was an important factor that must be considered. In this work, as a typical REBCO superconductor, YbBa2Cu3O7-delta (Yb123) was prepared by solid-state sintering in Ar (100 %), Ar (99.8 %)-O2 (0.2 %), Ar (99 %)-O2 (1 %), Ar (98 %)-O2 (2 %) and air atmospheres, and the effect of PO2 on the preparation of Yb123 was systematically investigated. The results showed that phase- pure Yb123 samples could be prepared in Ar (99 %)-O2 (1 %) at 1113 K and Ar (98 %)-O2 (2 %) at 1133 K, and the samples' critical transition temperatures were about 90 K. In contrast, Yb123 could not be formed in Ar (100 %) and Ar (99.8 %)-O2 (0.2 %) atmospheres, suggesting that there was a critical value of PO2 while preparing Yb123. Furthermore, the relationship between the PO2 and the optimum temperature range for synthesizing high phase-purity Yb123 could be quantitatively expressed as 30002/T =- lgPO2/Po + 24.9.