Improvement of critical parameters of YBa2Cu3O6.9 by low temperature treatment in the presence of water vapors

The effect of double thermal treatment at temperatures of 200 °C and 930 °C on the critical parameters of highly textured YBa2Cu3O6.9 ceramics has been examined. It has been shown that particles non-superconducting at T = 77 K, as well as planar stacking faults formed at low-temperature treatment in a humid atmosphere, are pinning centers of magnetic vortices. After recovery annealing (at 930 °C), the planar faults are partially preserved and serve as effective pinning centers in a magnetic field perpendicular to the c-axis. In addition, optimal double-annealing conditions have been found to significantly increase the critical current density up to the values jc ⩾ 104 A/cm2 in the external magnetic field (10 T), applied perpendicular to the c-axis.