Effects of Re-doping on microstructure and superconductivity of HgBa sub(2)Ca sub(2)Cu sub(3)O sub(8+ delta )

In order to study the solubility of Re in HgBa sub(2)Ca sub(2)Cu sub(3)O sub(8+ delta ) and the influence of Re-doping on microstructure and superconductivity, samples of Hg sub(1-x)Re sub(x)Ba sub(2)Ca sub(2)Cu sub(3)O sub(8+ delta ) with x identical with 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30, have been synthesized. Grain size and shape change with nominal Re content while the intra-grain microstructure which is dominated by stacking faults remains the same. Both, EDX and X-ray diffraction (XRD) measurements suggest a change of solubility of Re in HgBa sub(2)Ca sub(2)Cu sub(3)O sub(8+ delta ) at about x identical with 0.10-0.15 towards lower solubility. For x greater than or equal to 0.15 a Re-rich secondary phase appears. The critical temperature, T sub(c), of the Re-doped samples is above 130 K and the magnetic hysteresis, Delta M, shows a maximum for x identical with 0.15.