Influence of copper(II) sulfide addition on AC susceptibility and electrical properties of YBa2Cu3O7 superconductor

The effects of copper(II) sulfide (CuS) additions on the structure, electrical properties and AC susceptibility of YBa 2 Cu 3 O 7 (CuS) x superconductors for x = 0 to 5.0 wt. % were investigated. The solid state reaction method was used to prepare the samples. The non-added sample showed the highest onset temperature T c-onset (93 K) and zero-resistance temperature T c-zero (90 K). Addition of CuS lowered both T c-onset and T c-zero, and broadened the transition width. A double transition was observed in x ≥ 2.0 wt. % samples. This showed that CuS weakened the coupling between grains and suppressed the superconducting percolation leading to a double transition. The room temperature resistivity increased from 1.51 mΩ cm for x = 0 to 17.7 mΩ cm for x = 5.0 wt. %. The peak of the imaginary part of the susceptibility (χ”), T p shifted to lower temperatures with addition of CuS. The x = 1.0 wt. % sample showed the highest critical current density, J c ( T p = 69.5 K) of 24.1 A cm −2 .