Kilometer-long, coated conductor based HTS wires are now enabling many large-scale applications such as commercial nuclear fusion for energy generation as well as numerous other large-scale applications in the electric power industry and the defense industry. However, the price/performance metric of coated conductors is not yet favorable for most large-scale applications. The key to making the price/performance metric favorable is to significantly enhance the critical current density, Jc (H,T) of coated conductors.
We have previously reported excellent Jc’s and flux-pinning in YBCO films with self-assembled BZO columnar defects in the entire operating temperature regime from 4.2-77K via correlated pinning from extended defects at mid to higher operating temperatures as well as collective pinning from oxygen point defects arising due to the local micro-strain near YBCO/BZO interfaces at lower operating temperatures[1]. Here we report on our recent work to probe the limits of critical current density possible via defect engineering. We report on record values of critical current density, Jc, and pinning force, Fp, in REBCO coated conductors with self-assembled BZO nanocolumns fabricated using pulsed laser ablation. A Jc of ~175-180 MA/cm2 at self-field and ~80-85MA/cm2 at 7T was measured at 4.2K. At 20K, Jc of ~135-140 MA/cm2 at self-field and ~60MA/cm2 at 7T was observed. A very high pinning force, Fp, of ~6TN/m3 and ~4TN/m3 were observed at 4.2K and 20T respectively. These are the highest values of Jc and Fpreported to date. These results establish that significant performance enhancements are possible and hence the associated possible reduction in costs that could potentially be realized in optimized, commercial HTS wires. In addition, we have experimentally re-confirmed the effect of local micro-strain resulting in oxygen point defects due to the large lattice-misfit between REBCO and BZO as well as the effect of Ca-doping in REBCO coated conductors to mitigate the micro-strain. These results will help guide industry towards realizing significantly higher performance in commercial coated conductors.
[1] “Optimal, Nanodefect Configurations via Strain-Mediated Assembly for Optimized Vortex-Pinning in Superconducting Wires from 4.2K-77K”, A Goyal and S. H. Wee, Journal of Physics, 871 (2018) 012039.
[1] “Optimal, Nanodefect Configurations via Strain-Mediated Assembly for Optimized Vortex-Pinning in Superconducting Wires from 4.2K-77K”, A Goyal and S. H. Wee, Journal of Physics, 871 (2018) 012039.
Research support by the Office of Naval Research (ONR).