Comparative Study Between Similarly Processed
YBa₂Cu₃O_7-x Films with Y₂BaCuO₅ or BaSnO₃ Additions

C. V. Varanasi, J. Burke, L.Brunke,
J.H. Lee, H. Wang, P.N. Barnes

Abstract –   A special YBa₂Cu₃O_7-x (YBCO) target with a thin sector of second phase material, in this case either Y₂BaCuO₅ (Y211) or BaSnO₃ (BSO), was used to deposit YBCO films with non-layered nanoparticles on single crystal LaAlO₃ and biaxially textured Ni-5 wt.% W substrates buffered with CeO₂ and YSZ layers(coated conductors). Although identical processing conditions were used, TEM images indicated that random Y211 nanoparticles in the case of YBCO+Y211, and evenly spaced BSO nanocolumns in the case of YBCO+BSO, form in the YBCO films.  While YBCO plane buckling was observed at many places in the case of YBCO+Y211, a high density of stacking faults and dislocations were observed in the case of YBCO+BSO near the BSO columns.  In transport critical current density (J_c ) angular dependence  measurements, the absence of nanocolumns in YBCO+Y211 films resulted in the absence of a peak at 0°, J_c (H//c), in J_c vs. q plots,  as compared to a clear peak at 0o observed in YBCO+BSO films with the nanocolumns.  The in-field J_c measurements indicated small low-field J_c enhancements at 77 K in YBCO+Y211 films but more than an order of magnitude improvement in high-field J_c in YBCO+BSO films due to the differences in the microstructures.

Index Terms – BaSnO3, Coated conductors, Flux pinning, Pulsed laser ablation, Y211

Manuscript received 19 August 2008.
This work was supported by the AFOSR  and the Propulsion Directorate of the AFRL.
C. V. Varanasi, J. Burke, L.Brunke are with the University of Dayton Research Institute, Dayton, OH and Air Force Research Laboratory, WPAFB,OH  (e-mail:chakrapani.varanasi@wpafb.af.mil.)
J.H. Lee , H. Wang, are with Texas A&M University, College Station, TX, (email:wangh@mail.ece.tamu.edu)
P.N. Barnes is with the Air Force Research Laboratory, WPAFB, OH ( email paul.barnes@wpafb.af.mil)

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