Effect of structural water on the critical characteristics of highly textured YBa2Cu3O6.9

The effect of low-temperature treatment (200A degrees C) in a humid argon atmosphere and subsequent annealing (930A degrees C) on the critical parameters of a highly textured YBa2Cu3O6.9 has been studied. During annealing at T = 200A degrees C, the absorbed water is incorporated into the structure of the compound, which is accompanied by the deterioration of its superconducting properties. However, after the recovery annealing at T = 930A degrees C and subsequent oxidation, the superconducting characteristics (j (c) , B (1c) , and F (p) ) are improved. This is explained by the formation of 124-type planar defects, which are effective pinning centers, especially in high fields applied perpendicular to the c axis (aSyen c). The optimum conditions of double annealing substantially increasing the critical current density (j (c) a parts per thousand yen 10(4) A/cm(2)) in an external magnetic field up to 10 T and also the first critical fields have been found. In fields up to similar to T, the critical current density j (c) is isotropic despite the conservation of high texture in the samples.