We present a comparative study of the angular dependent critical current density in YBa 2 Cu 3 O 7 films deposited on IBAD MgO and on single crystal MgO and SrTiO 3 substrates. We identify three angular regimes where pinning is dominated by different types of correlated and uncorrelated defects. We show that those regimes are present in all cases, indicating that the pinning mechanisms are the same, but their extension and characteristics are sample dependent, reflecting the quantitative differences in texture and defect density. In particular, the more defective nature of the films on IBAD turns into an advantage as it results in stronger vortex pinning, demonstrating that the critical current density of the films on single crystals is not an upper limit for the performance of the IBAD coated conductors.

The influence of lattice strain and Mg vacancies on the superconducting properties of MgB2 samples has been investigated. High quality samples with sharp superconducting transitions were synthesized. The variation in lattice strain and Mg vacancy concentrations were obtained by varying the synthesis conditions. It was found that high strain (~1%) and the presence of Mg vacancies (~ 5 %) resulted in lowering the Tc by only 2 K.Comment: 3 figures, HTML+GIF format to be published in AP

We report significantly enhanced critical current densities (J c ) and flux pinning forces (F p ) in applied magnetic fields for YBa 2 Cu 3 O 7 (YBCO) films with embedded Ba 2 YNbO 6 (BYNO) nanorods. The films were grown by pulsed laser deposition with a target consisting of YBa 2 Cu 3 O y with five molar per cent additions of BaNbO y and Y 2 O 3 . With this composition, deposited films were found to contain a high density of BYNO nanorods that frequently traversed the entire thickness of the film (up to 1 μm), depending upon the deposition conditions. Enhanced J c performance occurs primarily for applied field orientations near the c-axis of the YBCO, which is nominally along the growth direction of the BYNO nanorods. The threading nanorod density of one film of the present work was measured by plan-view transmission electron microscopy to be 710-850 nanorods μm −2 . For approximately 1 μm thick films, typical J c (75.6 K, sf) and J c (75.6 K, 1 T c) values were ∼4.5 MA cm −2 and 1.3-1.5 MA cm −2 , respectively. For a 0.5 μm thick film, J c (75.6 K, 1 T c) > 2 MA cm −2 was achieved, and values of F p in excess of 30 and 120 GN m −3 were achieved at 75.5 K and 65 K, respectively.

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