SECOND PHASE (BaGeO₃, BaSiO₃) NANOCOLUMNS IN YBa₂Cu₃O_7-x FILMS

C. V. Varanasi^1,4, J. Reichart⁴, J. Burke^1,4,
H. Wang², M. Susner³, M. Sumption³, P.N. Barnes⁴

¹ University of Dayton Research Institute Dayton Dayton, OH, 45469-0170, USA
² Texas A&M College Station, TX, 77843-3128, USA
³ The Ohio State University Columbus, OH, 43210, USA
⁴ Air Force Research Laboratory Wright-Patterson AFB, OH, 45433, USA

ABSTRACT - YBa₂Cu₃O_7-x (YBCO) films with BaGeO₃ (BGeO), BaSiO₃ (BSiO) second phase additions were processed by pulsed laser deposition. Sectored targets with BGO or BSiO wedges as well as pre-mixed targets of YBCO, BGeO or BSiO with appropriate compositions were used to deposit YBCO+BGeO and YBCO+BSiO films on (100) single crystal LaAlO₃ substrates. The cross-sectional transmission electron micrographs showed the presence of 20 nm diameter nanocolumns in the YBCO films of both the compositions. However, the critical transition temperature (T_c) of the films was found to significantly decrease. As a result, the critical current density (J_c) in applied magnetic fields was suppressed. The YBCO+BGeO and YBCO+BSiO films made with lower concentrations of additions showed slight improvement in T_c indicating that the substitution of Ge and Si in the lattice is possibly responsible for the T_c depression. This study shows that in addition to the ability to form nanocolumns, the chemical compatibility of BaSnO₃ (BSO) and BaZrO₃ (BZO) as observed in YBCO+BSO and YBCO+BZO is critical to process high J_c YBCO films

KEYWORDS: Flux pinning, BaSnO3, BaGeO3, BaSiO3, YBa2Cu3O7-x, coated conductors, pulsed laser deposition

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IEEE/CSC & ESAS EUROPEAN SUPERCONDUCTIVITY NEWS FORUM (ESNF), No. 10, October 2009
On June 29, 2009, this manuscript was submitted for possible publication in “Advances of Cryogenic Engineering (Materials)"