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Second Phase (BaGeO3, BaSiO3) Nanocolumns in Yba2Cu3O7-x Films (Postprint)
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIR/POWER DIV/MECHANICAL ENERGY CONVERSION BRANCH
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YBa2Cu3O7-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 YBCOBGeO and YBCOBSiO 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 Tc of the films was found to significantly decrease. As a result, the critical current density Jc in applied magnetic fields was suppressed. The YBCOBGeO and YBCOBSiO films made with lower concentrations of additions showed slight improvement in Tc indicating that the substitution of Ge and Si in the lattice is possibly responsible for the Tc 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 YBCOBSO and YBCOBZO is critical to process high Jc YBCO films.
APPROVED FOR PUBLIC RELEASE