Enhancing Jc(B,theta) in YBa2Cu3O7-delta via nano-engineering of pinning structures
Issue Date
2009-04-29Author
Emergo, Rose Lyn S.
Publisher
University of Kansas
Format
131 pages
Type
Dissertation
Degree Level
Ph.D.
Discipline
Physics & Astronomy
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This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
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Critical current density (Jc) has been identified as one of the most critical parameters for the practical application of high temperature superconductors such as YBa2Cu3O7-δ (YBCO). Unfortunately, the Jc of optimized un-doped YBCO films barely satisfies the criteria for these applications. High J¬c can be achieved by introducing strong artificial pinning centers in YBCO which can inhibit flux motion and prevent dissipation. However, insertion of strong pins has been observed to strain and poison the YBCO lattice resulting in unnecessary degradation of Tc and low field Jc. In this work, two types of strong pinning centers with negligible effect on the Tc and low field Jc were incorporated in YBCO films via strain engineering on the nanoscale. The nanotube pores were generated by depositing YBCO films on vicinal SrTiO3 (STO) substrates. A close correlation between Jc and the magnetic pinning potential Up of the nanotube pores has been demonstrated below the accommodation field, suggesting that nanotube pores are strong pins on the magnetic vortices. Splayed BaZrO3 nanorords (BZO-NRs) were generated in YBCO film by depositing 2 vol.% BZO-doped YBCO on vicinal STO substrates. The interplay between the lattice strain caused by the large lattice mismatch between YBCO and BZO and the anisotropic strain due to vicinal growth resulted in the dispersed orientation of BZO-NRs. The splayed BZO-NRs led to an enhanced Jc in the entire range of the magnetic field orientation up to 5 T as compared to the non-splayed case of YBCO/BZO-NRs films.
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