Neutron powder diffraction study of the crystal structures of HgBa2CuO4+δ and HgBaO2

✍ Scribed by O. Chmaissem; Q. Huang; S.N. Putilin; M. Marezio; A. Santoro

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 344 KB
• Volume: 212
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(93)90587-g

✦ Synopsis

The crystal structures of HgBa2CuO4+a and HgBaO2 have been refined at room temperature using neutron powder diffraction data obtained from a sample containing 44% of the first phase, 42% of the second and 14% of Ba2Cu3Os+a. the compound Hg-Ba2CuO4+6 crystallizes with the symmetry of space group P4/mmm and lattice parameters a = 3.8829 (6), c= 9.5129 ( 14) A. The unit cell contains only one CuO2 layer and the material is a superconductor with a value of Tc of 94 K. The oxygen in excess of the 04 stoichiometry (6=0.063 in our sample) is located in interstitial positions on the HgOa layer, and it is the only extra oxygen present in the structure. No mixing of the cations has been detected in this study. The compound HgBaO2 crystallizes with the symmetry of space group R3m and lattice parameters (hexagonal axes ) a = 4.0991 (6), c= 19.355 (3)/~. In this new polymorph of HgBaOz the Ba atoms are octahedrally coordinated while Hg has two-fold coordination.