Synthesis and characterisation of HgBa2Ca0.7Dy0.3Cu2O6+delta

A new phase, HgBa2Ca0.7Dy0.3Cu2O6+delta, isostructural with HEBa2CaCu2O6+delta (Hg-1212), was synthesised by a precursor method in combination with high-temperature reactions (720 degrees C) in evacuated silica ampoules. The phase was the dominating one in the starting composition interval HgBa2Ca1-xDyxCu2O6+delta (0.3 less than or equal to x less than or equal to 0.6). The samples were characterised by X-ray powder diffraction, electron microscopy combined with energy dispersive spectrometry, susceptibility measurements, and IR spectroscopy. The tetragonal structure has the space group symmetry P4/mmm, and the unit cell parameters were refined to a = 3.8712(2) Angstrom and c = 12.5385(9) Angstrom. Carbon was detected in the samples by IR analysis, possibly stemming from oxy-carbonates but most likely from [CO](2+) groups in the Dy-doped Hg-1212 phase. The structure was refined by Rietveld analysis of the X-ray powder diffraction data and was compared with related 1212 compounds. Susceptibility measurements were performed on as-synthesized and oxygen-annealed samples. No superconducting transitions were found. (C) 1997 Elsevier Science S.A.