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

TLDR

The authors investigated how adding Ag or Ag₂O to YBa₂Cu₃O₇₋δ affects its mechanical and superconducting behavior, attributing strength gains to higher density, stress relaxation, and crack‑pinning by Ag particles, while noting that high Ag content introduces oxygen‑deficient nonsuperconducting phases that reduce critical current density. Adding 20 vol % Ag to YBa₂Cu₃O₇₋δ bars raised strength from ~40 to 75 MPa and doubled the critical current density, whereas 30 vol % Ag increased strength to 87 MPa but lowered Jc, with analogous trends observed for Ag₂O additions.

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.