Structure of Tl(Sr0.65Nd0.35)2CaCu2O7: Neutron powder diffraction study of cation ordering and oxygen stoichiometry

✍ Scribed by George H. Kwei; M.A. Subramanian

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 642 KB
• Volume: 168
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(90)90072-m

✦ Synopsis

The substituted 1212 thallium-based cuprate superconductor Tl(Sro.65Ndo.as)2CaCu20~ has been synthesized and found to have a transition temperature of 81 K at onset. The structure of this material has been refined using pulsed-neutron-powderdiffraction data collected at 295 K. The diffraction pattern was indexed to the space group P4/mmm and lattice parameters refined to a= 3.8282(3 ) and c= 11.9872(9) ,~. As in other T1 based perovskites, tetragonal displacements of the TI and O sites were required to model the distortions resulting from short-range ordering in the T1-O planes. In addition, we found substantial cation substitution at the Ca 2+ site, which presumably arises from disordering of Nd 3+ and Ca 2+ ions in their respective sites. Determination of the occupancies for the oxygen sites showed that they were essentially fully occupied.