A NEW MERCURY-BASED SUPERCONDUCTOR - (HG, CR)SR2CUOY

A new mercury-based cuprate superconductor, (Hg1-xCrx)Sr2CuOy (0 less-than-or-equal-to x less-than-or-equal-to 0.8),having T(c) of 58 K (x=0.3) has been synthesized. While a chromium-free sample (x=0) was multi-phased and the superconducting volume fraction was less than 1%, samples for x=0.3 and 0.4 were of nearly single phase and their superconducting shielding volume fraction reached 100% of perfect diamagnetism. X-ray diffraction analysis revealed, that its crystal symmetry was tetragonal with lattice parameters a0 = 3.840-3.8 54 angstrom and c0 = 8.639-8.705 angstrom which slightly varied with x. The observed co value, corresponding to the interlayer distance of superconducting CuO2 planes, was found to be the shortest among all the known mercury-based ''12 (n-1) n'' superconductors. Compared to the barium-containing compounds, the present barium-free materials have been found to be insensitive to the ambient air atmosphere during the synthesis and also to be quite stable after storage in air.