The dependence of transport critical-current density (Jc) on axial tensile strain (ε) was measured at 76 K and self-magnetic field for YBa2Cu3O7-δ (YBCO) coatings on buffered, deformation-textured substrates of pure Ni, Ni-5at.%-W, and Ni-10-at.%Cr-2-at.%-W. Expectations have been that the strain tolerance of these composites would be limited by the relatively low yield strains of the deformation-textured substrates, typically less than 0.2 %. However, results show that the irreversible degradation of Jcε occurs at a strain equal to about twice the yield strain of the substrate. Therefore, YBCO/Ni-alloy composites may satisfy axial-strain performance requirements for electric devices, including the most demanding applications, motors and generators in which a strain tolerance exceeding 0.25 % is needed. Furthermore, the YBCO/Ni-5-at.%-W conductors showed a reversible strain effect, which may be induced by a reversible strain-field broadening around mismatch dislocations at the grain boundaries. This effect may contribute to the unexpectedly large usable strain range of these conductors.
Citation: Applied Physics Letters
Pub Type: Journals
coated conductors, critical current density, elastic strain, mechanical properties, microstructure, reversibility, strain, stress, superconductors