A NEW 92-K HIGH-T(C) SUPERCONDUCTOR - HG-CONTAINING TL-BASED 1212 PHASE

Bulk superconductivity up to 92 K has been achieved in the mercury-containing curprate (Tl0.5Hg0.5)Sr2(Ca1-xYx)Cu2O7-delta when x = 0.3. Based on X-ray and electron diffraction and electron probe microanalyzer results, we identify the phase responsible for the superconductivity to be similar to that of (Tl0.5Pb0.5)Sr2CaCu2O7 (so-called 1212 phase) with a space group of P4/mmm and lattice constants of a approximately 3.8 angstrom and c approximately 12.0 angstrom. Moreover, neither superlattice nor intergrowth along the a* and c* directions were observed by electron diffraction. An increase in Ca2+ doping, 0.5 less-than-or-equal-to x less-than-or-equal-to 0.3, into the Y3+ sites results in a maximum superconducting transition temperature (T(c)) at around 92 K for x = 0.3. For compositions x < 0.3, a decrease in T(c) was observed.