Enhanced flux pinning and formation of Ba4Y2CuMoOy in top-seeded melt growth processed YBa2Cu3O7-d superconductors with Mo additions

The effect of Mo addition (0-10 wt%) on the superconductivity of top-seeded melt growth (TSMG) processed YBa2Cu3O7-y (Y123) superconductors was studied. The low level Mo addition (≤1 wt%) led to a small decrease of the superconducting transition temperature (Tc) and increase of the critical current density (Jc). The Jc improvement induced by the low level Mo additions appeared as a peak effect at the intermediated magnetic fields and peak position shift to the lower magnetic fields with increasing Mo content. The enhanced flux pinning caused by Mo additions seems to be attributed to the partial Cu substitution by Mo, YBa2(Cu1-xMox)3O7-d. The high level Mo additions (2-10 wt%), however, led to a large Jc decrease and broad superconducting transition due to the formation of low-Tc phases and the increased volume of the non-superconducting Mo-containing phase. The second particle phase formed by the high level Mo additions was identified as Ba4Y2CuMoOy (Mo4211) by x-ray diffraction (XRD) and scanning electron microscopy energy dispersive x-ray (SEM EDX) analysis.