Thin film nanocomposites based on YBCO with defects comprised of self-assembled inclusions

Abstract

Thin film nanocomposites based on YBCO with defects comprised of self-assembled inclusions Abstract. The critical current of YBCO superconducting coatings in external magnetic field can be enhanced by incorporating high density of extended nanometer-sized defects to act as pinning centers for magnetic vortexes. One particular variant involves the deposition superconducting film with columnar defects comprised of self-assembled BaZrO 3 , BaSnO 3 or BaHfO 3 nanoinclusions. Here we report the results of our study of YBCO films with different inclusions prepared by MOCVD. For the first time, we succeeded in growth of YBCO films with oriented nanoinclusions of BaCeO 3 phase and demonstrate that it does not reduce T c of YBCO, in contrast to BaZrO 3 or BaSnO 3 . The best composite thin films revealed the T c value of about 88K and critical current density at 77K above 1MA/cm 2 in self-field and around 0.3 MA/cm 2 in 1 T (B//c).

Anisotropic strain of BaZrO3, BaCeO3and Y2O3nanoinclusions in a YBa2Cu3O7 −xepitaxial film matrix and its relation to the oxygen content of the superconductor

“…In this paper we present our observations on the strained nature of BaZrO 3 (BZO), BaCeO 3 (BCO) and Y 2 O 3 inclusions in epitaxial YBCO matrix obtained by metal oxide chemical vapour deposition (MOCVD). Some previous observations were reported in earlier papers [12,13]. We argue that significant anisotropic strain observed in BZO, BCO and Y 2 O 3 is caused by unusually large shrinkage of the YBCO lattice along its c-axis at a low temperature oxygenation step.…”

“…The results of the x-ray study of YBCO films with different amounts of inclusions can be found in our earlier reports [12,13]. In this study we concentrate on two samples with 10 mol% (approximately 6 wt%) of either BZO or BCO addition.…”

“…All thin films were grown by MOCVD as described elsewhere [12,13]. Metal chelates with 2,2,6,6-tetramethylheptanedione-3,5 were used as volatile complexes to obtain these films.…”

“…The reduction of T c was argued to be due to strain [9] or formation of secondary phases along with increased global cation disorder in YBCO [10,11]. It can be also due to strain-induced oxygen deficiency of YBCO, partial zirconium substitution into the YBCO lattice [11][12][13] or combination of all these effects. A general consensus is still lacking and more studies are needed to clarify this issue.…”