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Epitaxial YXBa2Cu3O7-δ (YXBCO) thin films were deposited by pulsed laser deposition on both single crystal SrTiO3 (100) and buffered polycrystalline metal substrates, where X=0.9, 1.0, 1.1, 1.2, and 1.3. The self-field critical current density (Jc) of YXBCO exhibits the best performance at X=1.1 for the samples on both single crystal substrates and metal substrates. Epitaxial Y2O3 nanoparticles were observed in Y-rich samples (X>1.0) by X-ray diffraction and cross-sectional transmission electron microscopy. The field-dependence and angular-dependence measurements show that Y2O3 nanoparticles improve the in-field Jc performance, especially in the low field regime, without reducing self-field Jc of YBCO films. [ABSTRACT FROM AUTHOR]

We conducted a comparative study of microstructural properties for YBa2Cu3O7 (YBCO) films on single-crystal MgO and polycrystalline Ni-based metal substrates with ion-beam-assisted deposited (IBAD) MgO as a template. The film grown on the metal substrate shows more crystalline imperfections with density of screw dislocations four times higher than that of the film on single-crystal MgO, as revealed by high-resolution x-ray diffraction (HRXRD). These high-density screw dislocation cores connect well and form bigger clustered grains as detected by scanning tunneling microscopy. Transmission electron microscopy studies confirm that the structural quality of YBCO on the Ni-based alloy is comparable to that on single-crystal MgO. All these factors contribute to our routine fabrication of high-quality YBCO films on metal substrates with critical current densities in self-field as high as those for the films grown on single-crystal MgO substrates. Superconducting properties in fields are also discussed. [ABSTRACT FROM AUTHOR]

We compare the angular-dependent critical current density (J[sub c]) in YBa[sub 2]Cu[sub 3]O[sub 7] films deposited on MgO templates grown by ion-beam-assisted deposition (IBAD), and on single-crystal substrates. We identify three angular regimes in which pinning is dominated by different types of correlated and uncorrelated defects. Those regimes are present in all cases, but their extension and characteristics are sample dependent, reflecting differences in texture and defect density. The more defective nature of the films on IBAD turns into an advantage as it results in higher J[sub c], demonstrating that the performance of the films on single crystals is not an upper limit for the IBAD coated conductors. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

One of the most intensely researched subjects in the development of YBa[SUB2]Cu[SUB3]O[SUB7-δ] (YBCO)-based coated conductors is the methodology for achieving ever-sharper film texture on flexible metal substrates. This is a critical issue due to the intrinsic weak-link behavior that results in depressed critical current density (J[SUBc]) in polycrystalline YBCO. Using ion-beam-assisted deposition of magnesium oxide, we have achieved YBCO texture on superalloy substrates approaching that on single-crystal oxide substrates. This advance has allowed us to fabricate coated conductor samples with J[SUBc]S that are as high as for films on oxide crystals; for example, >2 MA/cm[SUP2] (75 K, self-field) at a YBCO thickness of ∼1.5 μm. [ABSTRACT FROM AUTHOR]