Study of the Flux Pinning Landscape of YBCO Thin Films With Single and Mixed Phase Additions BaMO3 + Z: M = Hf, Sn, Zr and Z = Y2O3, Y211

Mary Ann P Sebastian,Wenrui Zhang,Charles R Ebbing,George Y Panasyuk,Margaret M Ratcliff,Haiyan Wang,Jack L Burke,Jijie Huang,Joshua N Reichart,Thomas J Bullard,Judy Wu,Chen-Fong Tsai,Timothy J Haugan

doi:10.1109/tasc.2017.2652301

Abstract

Addition of nanophase defects to YBa2Cu3O7 (YBCO) superconductor thin films enhances flux pinning, resulting in an increase in transport current densities (Jct). While previous studies focused on single-phase additions such as BaSnO 3 , BaZrO 3 , and Y 2 BaCuO 5 (Y211); the addition of several phases simultaneously has shown strong improvements by combining different flux pinning mechanisms. This paper further explores and compares the effect of mixed-phase nanoparticle pinning, with the addition of insulating, nonreactive phases of: 1) BaSnO 3 + Y 2 O 3 , 2) BaSnO 3 + Y211, 3) BaZrO 3 + Y 2 O 3 , and 4) BaHfO 3 + Y 2 O 3 . Processing parameters vary the doped YBCO single target volume percent of either BaHfO 3 , BaSnO 3 , or BaZrO 3 , while maintaining either Y 2 O 3 or Y211 constant at 3 vol.%. Pulsed laser deposition produces films on LaAlO 3 and SrTiO 3 substrates at deposition temperatures of 750-840 °C. Current density is measured for fields ranging from H = 0-9 T with H // c, and temperatures from 5 to 77 K, providing a detailed picture of pinning effects. Optimized results of flux pinning, magnetic current densities J cm (H, T), critical transition temperatures (T c ), lattice parameters, and microstructures are presented. The temperature dependence of the current density, J c (T), is mathematically modeled to compare the isotropic weak and anisotropic strong pinning contributions, for each of the mixed phase systems studied.

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