SUPERCONDUCTIVITY ABOVE 120-K IN HGBA2CACU2O6+DELTA

The second member (Hg-1212) of the recently discovered homologous series HgBa2Can-1CunO2n+2+delta has been synthesized by solid state reaction, carried out at 800-degrees-C under 60 kbar. The X-ray diffraction powder pattern of one of the samples was refined by the Rietveld analysis. The final results clearly showed that it corresponded to the structural arrangement of the Hg-1212 compound with lattice parameters a = 3.85 56 (8) angstrom, c = 12.652 (4) angstrom. No major impurities were observed in the X-ray pattern. AC magnetic susceptibility measurements showed that these samples undergo a paramagnetic-to-diamagnetic transition well above 120 K. The multi-transition aspect of the susceptibility curves showed that the samples contained some intergrowth. In a few samples a transition as high as 132 K was observed which might correspond to the third member of the Hg-series.