The high-Tc YBa2Cu3O7-δ composite superconductors containing Zr, Ag and Y2BaCuO5 have been fabricated by melt processing. Both the critical current density JMc and the flexural strength αmax of these samples were measured. The value of JMc 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 JMc. The largest value of JMc we obtained is 64 800 A/cm2 on the sample containing 50 mol.% Y2BaCuO5. In contrast, the value of αmax was limited below 60 MPa due to the presence of mechanically weak grain boundaries. The addition of Ag to YBa2Cu3O7-δ was effective in increasing both αmax and JMc.
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