High critical current density in Y–Ba–Cu–O bulk superconductors with very fine Y211particles

Abstract

We have succeeded in enhancing the critical current density(Jc) of melt-textured Y–Ba–Cu–O superconductors by employing ultra-fine Y211powder as precursor. The Y211 starting powders were reduced down to 110 nmin diameter with ball-milling. Single-grain Y–Ba–Cu–O samples up to 33 mm indiameter were fabricated from the precursors containing finely milled Y211powders. The Y211 inclusions in the melt-textured samples could be refined bydecreasing the particle size of the Y211 starting powders. The maximum value ofJc at 77 Kwas 1.1 × 105 A cm−2 in a self-field. However, the size reduction of Y211 led to an inhomogeneous distribution ofY211 particles, in which the volume fraction of the Y211 phase greatly decreased near aseed crystal. An Ag-added bulk sample 33 mm in diameter exhibited a high trappedmagnetic field of 1.6 T at 77 K.