Temperature and Magnetic Field Dependence of Critical Current Density of YBCO With Varying Flux Pinning Additions.

The critical current density (J_c) of YBa₂Cu₃O_7-z films doped with varying flux pinning nanoparticle additions was systematically studied, for applied magnetic fields of H = 0-9 T and operation temperatures T = 20-77 K. Films were prepared with pulsed laser deposition by (M/YBCO)_N multilayer or (YBCO)_1-xM_x single-target methods, for different M phases including Y₂O₃, Y₂BaCuO₅ (Y211) green-phase, and BaZrO₃. Very significant differences of J_c(H//c, 20 - 77 K) were measured for optimized M phase additions, that are difficult to model or predict at present. Multilayer films with Y211 and Y₂O₃ nanoparticle additions had the highest J_c(20 - 77K) for H < 4 T, and YBCO+BZO-nanorod samples had the strongest J_c(H) for H > 4 T and 65-77 K, however not for T < 50 K. Seemingly unusual J_c(H, T) properties were measured for (BZO/YBCO)N multilayer films when compared to YBCO and other doped films; J_c(H) was almost the same as YBCO at 77 K, however at 30 K J_c(H > 2 T) had the strongest properties increasing 70% compared to YBCO+nanoaddition films and increasing 400% compared to YBCO. [ABSTRACT FROM AUTHOR]