The Effect of Sm Addition on the Microstructure and Superconducting Properties of YBCO Bulk Superconductors

The effect of Sm addition on the microstructure and superconducting properties of Y-Ba-Cu-O (YBCO) bulk superconductors has been studied. Nominal composition: 1 mol YBa2Cu3O7-delta+ 0.25 mol Y2O3+ 1 wt% CeO2 was enriched with different amounts of SmBa2Cu3Oy powder with the aim to increase critical current density, J(c), especially in higher magnetic fields by introducing additional pinning centers. Single grain YBCO bulk superconductors with SmBa2Cu3Oy (Y123-Sm) addition were prepared by the optimized top seeded melt growth process. Microstructure analysis, performed by polarized light microscope, revealed that SmBa2Cu3Oy addition leads to a higher amount of slightly coarser Y2BaCuO5 particles, which is related to lower critical current densities (J(c) approximate to 6 x 10(4) A/cm(2)) of the YBCO samples with SmBa2Cu3Oy addition in low magnetic fields. On the other hand, an enhancement of critical current density, J(c), in higher magnetic fields was observed for Y123-Sm samples. Moreover, a maximum trapped magnetic field, B-tmax, of 564 mT at 77 K in Y123-Sm, x = 0.0025 sample ((empty set)17.2 mm) was 43% higher than that for YBCO sample without any addition.