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

Abstract

GdBa 2 Cu 3 O 7-y (Gd123) powders were synthesized by the solid-state reaction method using Gd 2 O 3 (99.9% purity), BaCO 3 (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with Gd 2 O 3 addition (Gd 1.5 Ba 2 Cu 3 O 7-y (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 (T c,onset ) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The T c,onset of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density (J c ) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/cm 2 . The addition of 0.25 mole Gd 2 O 3 and 1 wt.% CeO 2 to Gd123 enhanced the T c , J c 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 T c of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The J c s at 77 K (0 T and 2 T) were 3.2 × 10 4 A/cm 2 and 2.5 × 10 4 A/cm 2 , 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).