Effects of Ag Addition on Superconductivity and Microstructure of DyBa₂Cu₃O_7-δ-Ag Composite

This paper reports on the effects of Ag addition on physical properties of high temperature superconductors DyBa2Cu3O7-δ (Dy123). A series of the Dy123 - Agx composite was prepared by solid state reaction method with varying amount of metallic silver (x = 0 – 0.3). Resistance versus temperature measurement was done using the four-point-probe method in the temperature range of 79 K to 300 K. Pure DyBa2Cu3O7-δ was found to superconduct with Tc onset of 91 K and Tc zero of 78 K. Addition of Ag at x = 0.05 caused both Tc onset and Tc zero to increase to 93 K and 84 K, respectively. However, Tc onset and Tc zero dropped for higher silver contents. We found that the optimum silver content in DyBa2Cu3O7-δ for best superconducting behavior and hardness is between x = 0.05 and 0.10. Microstructure analysis using SEM and EDAX showed that most of the silver is uniformly distributed along the grain boundaries filling the pores and hence increasing the hardness of the samples.