Structural and Superconducting Properties of Hg0.75Re0.25Ba2-xSrxCa2Cu3O8+delta Superconductors Grown by Sol–Gel and Sealed Quartz Tube Synthesis

The structural and superconducting properties of Hg0.75Re0.25Ba2-xSrxCa2Cu3O8+delta (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) grown by sol–gel and sealed quartz tube synthesis were investigated through XRD, EDX, and micro-Raman analysis. They show that the efficiency of c-axis reduction caused by the Sr substitution depends on the environment in the (Hg,M)–O layer. The rhenium doping produces a more rigid block that limits the Sr substitution in the Ba site more than other reported doping cations, such as lead. Superconducting properties measurements show that the irreversibility line (IL) values decrease with increasing Sr substitution. Moreover, the IL line measurements also show that the vortex lines have a 3D behavior for all the samples with n values in the range 2.1–1.9. Finally, resistivity measurements under high pressure indicate an overdoped regime for these samples.