Superconductivity up to 110 K in the 1212-Hg based cuprate Nd1-xCaxBa2Hg1-x'Cu2+x'O6+y

A mercury based superconductor Nd 1− x Ca x Ba 2 Hg 1− x Cu 2+ x' O 6+ y , with a T c (onset) of 110 K has been synthesized for 0.4≤ x ≤0.6 and 0≤ x' ≤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 Y 0.6 Ca 0.4 Ba 2 Cu 2 Hg 1− x M x O 6+ 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.