Nano-composite single grain YBa2Cu3O7-δ / Y2Ba4CuBiOy bulk superconductors

We have succeeded recently in synthesizing a chemically stable, inert family of materials of composition Y2Ba4CuMOy (Y-2411 where M = Nb, Ta, Mo, W, Zr, Hf) within the superconducting YBa2Cu3O7-δ• (Y-123) phase matrix that forms effective flux pinning centers of nano-scale dimensions. In this paper we report the synthesis of the Y2Ba4CuBiOy phase with nano-scale dimensions that is similarly compatible with the Y-123 matrix and which does not impair the properties of the bulk superconductor. YBa2Cu3O7-δ / Y2BaCuO5 (Y-123/Y-211) precursor powders enriched with various amounts of Bi 2 O 3 and Y2Ba4CuBiOy have been fabricated successfully in the form of large, single grains by the top seeded melt growth (TSMG) process. Microstructural studies of these composites reveal the presence of nanometer-sized Y2Ba4CuBiOy and much larger Y-211 phase particles (~ 1 μm) embedded in the Y-123 phase matrix. The critical current density of the nano-composites is observed to increase significantly compared to undoped YBCO.