Critical current density and mechanical strength of YBa₂Cu₃O_7-δ superconducting composites containing Zr, Ag and Y₂BaCuO₅ dispersions by melt-processing

The high-T_c YBa₂Cu₃O_7-δ composite superconductors containing Zr, Ag and Y₂BaCuO₅ have been fabricated by melt processing. Both the critical current density J^M_c and the flexural strength α_max of these samples were measured. The value of J^M_c increased initially for all inclusions added. The microstructure analyses revealed that the Y₂BaCuO₅, Ag and BaZrO₃ were finely dispersed in the matrix. We believe that the fine dispersion of these inclusions is most likely responsible for an increase in J^M_c. The largest value of J^M_c we obtained is 64 800 A/cm² on the sample containing 50 mol.% Y₂BaCuO₅. In contrast, the value of α_max was limited below 60 MPa due to the presence of mechanically weak grain boundaries. The addition of Ag to YBa₂Cu₃O_7-δ was effective in increasing both α_max and J^M_c.