SUPERCONDUCTIVITY UP TO 110-K IN THE 1212-HG BASED CUPRATE ND1-XCAXBA2HG1-X'CU2+X'O6+Y

A mercury based superconductor Nd1-xCaxBa2Hg1-x'Cu2+x'O6+y, with a T(c) (onset) of 110 K has been synthesized for 0.4 less-than-or-equal-to x less-than-or-equal-to 0.6 and 0 less-than-or-equal-to x' less-than-or-equal-to 0.2. No high pressure was used for the synthesis. The X-ray and high resolution electron microscopy studies show that the material exhibits the ''1212''-structure, i.e. it is isotypic with the 90 K superconductor Y0.6Ca0.4Ba2Cu2Hg1-xMxO6+y. The X-ray micro-analysis shows a dramatic variation of the distribution as well as of the content of the cations between different crystals of the same sample; this might explain the broad character of the transition. The possibilities for improving the superconducting properties of this material are discussed.