HIGH-PRESSURE SYNTHESIS AND PROPERTIES OF THE HGBA2CAN-1CUNO2N+2+DELTA (N=1-6) SUPERCONDUCTORS

High-pressure high temperature synthesis has allowed us to prepare members of the new superconducting mercury cuprates series with n=1-6. The variation of the structural and magnetic properties, oxygen content and T-c across the series, which appears to be the richest among the different superconducting cuprates, will be presented and discussed. T-c and the oxygen content delta increases with n from Hg-1201 (T-c=95K, delta=0.06) to a maximum of 135 K with delta=0.40 for Hg-1223. Structural refinement from neutron diffraction data on Hg-1245 showed a further decrease of delta=0.30 in the high pressure as prepared compound (T-c=101K). Tentatives to increase delta by a treatment under 200 bar of oxygen in Hg-1234, Hg-1245 and Hg-1256 showed instead a loss of oxygen from the overdoped as prepared samples