Synthesis and properties of superconducting HgBa2CuO4+xfrom a single-step low-temperature solid state reaction

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Abstract
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 Tc of 95 K, as obtained by the diamagnetic onset and resistivity measurements. The crystal symmetry was tetragonal with lattice parameters a=3.876(1) AA, and c=9.509(4) AA 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.