TRANSPORT AND MAGNETIC-PROPERTIES OF YBCO/AG COMPOSITES

The transport and magnetic properties of pure Y-Ba-Cu-0 and Y-Ba-Cu-O/Ag composites prepared by the co-precipitation method have been studied. The normal state resistivity decreases with addition of silver. The magnetic properties reveal that addition of silver to the YBCO sample degrades the superconducting properties. However, the increase in transport critical current density both at 77 and 4.2 K suggests the presence of proximity junctions (SNS) at the intergranular regions. The magnetic critical current density is reduced and the magnetization hysteresis loops measured at both 77 and 4.2 K shrink with addition of silver, indicating changes in the inter- and intragranular properties. The flux creep rate increases and the activation energy calculated from the relaxation data (5.5 T) at 4.2 K decreases with increasing silver concentration, showing a reduction in the number of pinning centres.