Influence of Oxygen Concentration and Distribution on Microstructure and Superconducting Characteristics of MgB 2 -Based Materials and Melt-Textured YBCO.

The oxygen concentration and distribution in the microstructure of MgB2- and YBa2Cu3O7-δ-based materials affect the formation of nanostructural defects and thus influence the critical current density, upper critical magnetic field and irreversibility field. For MgB2 oxygen containing additions (Dy-O, Ti-O) in the form of nanograins occurred not to be very effective for an increase of critical current density, jc. Sn-O additions to MgB2 can provoke even a significant decrease of jc due to a chemical interaction of Sn with MgB2. The processing pressure and temperature influence the defect density of the relevant pinning centers and the regularity of their distribution in doped and undoped MgB2 as well as in MT-YBCO. [ABSTRACT FROM AUTHOR]