Effect of silver and silver oxide additions on the mechanical and superconducting properties of YBa2Cu3O7−δ superconductors

Abstract

The effects of Ag and Ag₂ O additions on the mechanical and superconducting properties of YBa₂ Cu₃ O_7−δ superconductors were studied. The addition of 20‐vol % Ag resulted in an increase in strength from ≊40 to 75 MPa and a twofold increase in the critical current density (J_c ) of YBa₂ Cu₃ O_7−δ bar specimens. These improvements are believed to be due to the increased density. Furthermore, Ag particles may relax the residual stresses resulting from the expansion anisotropy of individual grains, and may provide increased resistance to crack propagation by pinning the propagating cracks; these effects would also increase the strength. The addition of 30‐vol % Ag resulted in an increase in strength to 87 MPa, but it was associated with a decrease in J_c . This decrease in J_c at high Ag content is believed to be due to the presence of oxygen deficient nonsuperconducting tetragonal phase as well as continuous Ag phase. Similar effects were also observed after Ag₂ O additions.