A combined powder melt and infiltration growth technique for fabricating nano-composited Y−Ba−Cu−O single-grain superconductor

Abstract

The top-seeded melt growth (MG) and infiltration growth (IG) techniques are the two most popular methods of fabricating single-grain Y−Ba−Cu−O (YBCO) bulk superconductors, which are also considered as two distinctly different processes. In this study, we report a combined powder melt and infiltration growth (PM-IG) technique for fabricating nano-composited YBCO single-grain superconductors using raw metallic oxides. In this new technique, a solid source pellet (SSP) of composition nano-Y2O3 + BaO + CuO + 1 wt.%CeO2 and a liquid source pellet (LSP) of composition nano-Y2O3 + 10BaO + 16CuO are employed, thus during heat treatment process the powder melt in SSP (corresponding to the final YBCO bulk) and liquid infiltration from LSP to SSP coexist. Because the process of precursor powder synthesis is avoided, the fabrication flow is much simplified and the experimental efficiency is increased significantly. Microstructural observation indicates that a large number of Y2BaCuO5 nano-inclusions (around 100 nm) are trapped in the YBa2Cu3O7−δ superconducting matrix. Measurements of levitation force and trapped field prove the superior performance of the nano-composited YBCO sample. The calculated zero-field Jc at 77 K reaches 6.98 × 104 A cm−2, nearly 23% higher than the sample fabricated by the conventional IG technique. Thus, this study supplies a practical method for fabricating nano-composited YBCO bulk superconductors with high performance.