INFLUENCE OF PARTIALLY DOUBLE SUBSTITUTIONS ON THE SUPERCONDUCTIVITY OF MERCURY-CUPRATES

The electrical conductivity changes of polycrystalline mercury-cuprate s by partial substitutions of Hg by Pb + Cd, Tl + Cd and Tl + Pb in th e temperature range between 77 and 300 K have been measured. Whereas s ingle substitution of Hg by Cd alone yet at low concentrations destroy s the superconductivity of the mercury-cuprates, high zero resistance transition temperature T-c0 = 128 K has been obtained for samples with the nominal composition Hg0.7Pb0.15Cd0.15Ba2Ca2Cu3O8-x. The sample co mpositions have been controlled by EDX, their microstructure was inves tigated by X-ray diffraction and SEM.