High-pressure synthesis and superconducting properties of the oxychloride superconductor(Sr,Ca)3Cu2O4+δCl2−y

Abstract

Chlorine-containing (Sr,Ca)(3)CU2O4+deltaCl2-y superconductors have been synthesized at 5.0 Ga and similar to 1000 degrees C. The double-[CuO2] layered compound crystallizes into (La,Sr)(2)CaCu2O6 structure with Cl residing at the apical anion site relative to the [CuO2] plane. The critical transition temperature T-c 80K has been achieved in these superconductors. The Sr2.3Ca0.7Cu2O4+deltaCl1.3 superconductor was studied in terms of irreversibility field Hi, and intragrain critical current density I,. It is found that the irreversibility field of the superconductor can be described by the power law dependence (I-T/T-c)(n), with n similar to 2. The reduced H-irr(T/T-c) line is positioned between those of YBa2Cu3O7 and Bi2Sr2CaCu2O8 in the H-T plane, close to HgBa2CaCu2O6+delta. The critical current density J(c)(T) was extracted from the Bean critical-state model and showed a smooth temperature dependence. No significant difference was found for the general behavior of H-irr(T) and J(c)(T) of (Sr,Ca)(3)Cu2O4+deltaCl2-y from those of oxide high-T-c superconducting cuprates (HTSC). The off-plane space remains the important parameter to evaluate interlayer coupling of the oxyhalide HTSC, which is consistent with oxide HTSC. The results suggest the potential application capability of the oxyhalide superconductors even though the off-plane block is composed of oxyhalide instead of the routine oxides.