SYNTHESIS AND PROPERTIES OF SUPERCONDUCTING HGBA2CUO4+X FROM A SINGLE-STEP LOW-TEMPERATURE SOLID-STATE REACTION

A novel technique based on a low-temperature single-step solid state reaction of stoichiometric quantities of HgO and Ba2CuO3 to produce superconducting HgBa2CuO4+x samples has been developed. The `as-prepared' polycrystalline Hg-1201 samples had a T-c of 95 K, as obtained by the diamagnetic onset and resistivity measurements. The crystal symmetry was tetragonal with lattice parameters a = 3.876(1) Angstrom, and c = 9.509(4) Angstrom in agreement with literature data. Sample morphology consists of grains (average dimension 30 mu m) larger than in previously published works and of a needle-like structure embedding the whole sample. These results were highly reproducible over several batches. The resistive transition in magnetic field up to 8 T and a set of magnetic measurements is presented. From these measurements we obtain information about the irreversibility line, the critical current field dependence and the presence of weak links.