Superconducting Tl2.0Ba2.0CuO6+δ: A high resolution neutron powder and single crystal x-ray diffraction investigation

✍ Scribed by J.B. Parise; C.C. Torardi; M.A. Subramanian; J. Gopalakrishnan; A.W. Sleight; E. Prince

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 437 KB
• Volume: 159
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(89)90375-4

✦ Synopsis

The structure of the orthorhombic form of T12Ba2CuO6+a( To= 90 K), synthesized in sealed gold tubes using BaO2, has been refined using high resolution neutron powder diffraction data collected at 4 K. No significant deficiency in metal stoichiometry could be inferred from the crystal structure analysis. The space group (Fmmm) used in this study gives essentially the same results as the alternatives (Abma, Amaa) proposed in earlier work. The large amount of disorder that exists in the Tl202-siab is mirrored in the large thermal parameters for this structural unit compared to those for the CuO2 sheet. A site at ( ~ ~ 41 ) is occupied by an amount of oxygen to give overall stoichiometry TleBa2CuO6 l o, suggesting that oxygen non-stoichiometry plays an important role in producing high Tc superconductivity in this system. Analysis of single crystal X-ray diffraction data oftetragonal T12BazCuO6 + 6 is totally consistent with the neutron powder diffraction results.