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

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Abstract
The effects of Ag and Ag2 O additions on the mechanical and superconducting properties of YBa2 Cu3 O7−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 (Jc ) of YBa2 Cu3 O7−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 Jc . This decrease in Jc 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.