Fabrication of Gd1.5Ba2Cu3O7-y Bulk Superconductors from the Powder Synthesized by a Solid-State Reaction Method

Abstract

<TEX>$GdBa_2Cu_3O_{7-y}$</TEX>(Gd123) powders were synthesized by the solid-state reaction method using <TEX>$Gd_2O_3$</TEX> (99.9% purity), <TEX>$BaCO_3$</TEX> (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with <TEX>$Gd_2O_3$</TEX> addition (<TEX>$Gd_{1.5}Ba_2Cu_3O_{7-y}$</TEX>(Gd1.5)) were used as raw powders for the fabrication of Gd123 bulk superconductors. The Gd123 and Gd1.5 bulk superconductors were fabricated by sintering or a top-seeded melt growth (TSMG) process. The superconducting transition temperature (<TEX>$T_{c,onset}$</TEX>) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The <TEX>$T_{c,onset}$</TEX> of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density (<TEX>$J_c$</TEX>) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/<TEX>$cm^2$</TEX>. The addition of 0.25 mole <TEX>$Gd_2O_3$</TEX> and 1 wt.% <TEX>$CeO_2$</TEX> to Gd123 enhanced the <TEX>$T_c$</TEX>, <TEX>$J_c$</TEX> and magnetic flux density (H) of the TSMG processed Gd123 sample owing to the formation of the superconducting phase with high flux pinning capability. The <TEX>$T_c$</TEX> of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The <TEX>$J_cs$</TEX> at 77 K (0 T and 2 T) were <TEX>$3.2{\times}10^4\;A/cm^2$</TEX> and <TEX>$2.5{\times}10^4\;A/cm^2$</TEX>, respectively. The H at 77 K of the TSMG-processed Gd1.5 was 1.96 kG, which is 54% of the applied magnetic field (3.45 kG).