4, University of Dayton Research Institute, Dayton, Ohio, United States
2, U. of Kansas, Lawrence, Kansas, United States
3, Purdue University, W. Lafayette, Indiana, United States
The addition of nanosize defects to YBa2Cu3O7-z (Y-Ba-Cu-O or YBCO) superconductor thin films have been studied by many groups world-wide, to enhance flux pinning and strongly increase critical current densities (Jcs). Since the first publications of this field in 2003 and 2004, over 6,200 citations have been listed for the subfield ‘flux pinning YBCO’, and the subfield ‘flux pinning’ has over 60,000 citations (source, Google Scholar). Despite many excellent systems studied, there are still new types of defect additions, flux pinning mechanisms, and processing methodologies to explore. This paper reviews and summaries studies in our lab from 2003 to 2018 on multiple YBCO+M+N systems, and presents recent interesting results on YBCO+Y2BaCuO5 films, achieving to our knowledge the largest defect sizes > 40 nm in YBCO-films so far. The pinning of this system is surprisingly different, by attaining > 10 vol% additions and strongly enhancing both strong anisotropic and weak isotropic pinning simultaneously. Thin films were made by pulsed laser deposition of (M/YBCO)X multilayer and (YBCO)1-x(M,N)x single-target films. Results and comparisons of flux pinning for different realms of T = 4-77 K, H = 0-9 T, and Theta = 0-90 degrees will be presented, and correlated with microstructure studies.
This work was supported by the AFRL Aerospace Systems Directorate and the Air Force Office Scientific Research (AFOSR).