X-ray single crystal structure analysis of the 1245 type superconductor Hg0.5Pb0.5Ba2Ca4Cu5O12+δ

✍ Scribed by H. Schwer; J. Karpinski; L. Lesne; C. Rossel; A. Morawski; T. Lada; A. Paszewin

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 603 KB
• Volume: 254
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(95)00576-5

✦ Synopsis

Crystals of Hgo.sPbo.sBa2Ca4CusO12+ 8 were measured on an X-ray four-circle single-crystal diffractometer and the crystal structure was refined to R -0.033. The onset of the superconducting transition of the crystals ranges from 101 K-115 K. The space group is P4/mmm and lattice parameters of the five-layer material are a = 3.8529(3) ~,, and c = 22.172(2) ,~. Hg is partially substituted for Pb and heavy atoms are shifted away from the origin by ~ 0.38 A. Stacking faults of 1234 or 1256 material are manifest in the Fourier maps, and the amount was refined to 4.4%. These stacking faults induce an additional electron density at the ideal 0(4) site and mask a possible oxygen occupancy at (½, ½, 0). However, electron density is observed at a distance of 0.6 ,~ from (½, -~, 0), suggesting a shift of the excess oxygen atom from its ideal position. Bondlengths and distances show systematic changes with increasing number n of CuO 2 layers. Changes occur mainly in the rock-salt type layer, whereas the CaCuO 2 units remain stable over the whole Hg-12(n -1)n series.