A NEW CUPRATE WITH MERCURY BILAYERS - THE 2222-OXIDE HG(2-X)M(X)BA(2)PR(2)CU(2)O(10-DELTA) (M=CU, PR)

A ''2222'' cuprate with mercury bilayers (Hg1.5Cu0.2Pr0.3)Ba2Pr2Cu2O10 -delta, has been synthesized for the first time. It crystallizes in th e P4/nmm space group with a = 3.9072(1) Angstrom and c = 17.219(1) Ang strom. The powder XRD and HREM studies of this new cuprate show that i ts structure consists of an intergrowth of double pyramidal (oxygen-de ficient perovskite) copper layers, with double fluorite-type layers an d distorted triple rock salt layers (mercury bilayers). The structure of this phase can be deduced from that of the ''2212'' mercury cuprate (Hg1.5Cu0.2Pr0.3)Ba2PrCu2O8-delta by the introduction of one addition al [PrO2]infinity fluorite layer. The regular stacking of the metallic layer and the uniform cationic distribution in the mercury bilayers a re remarkable features of this cuprate. The stabilization of the mercu ry bilayers by praseodymium and the absence of superconductivity are d iscussed. (C) 1995 Academic Press, Inc.