Electron microscopy of superconducting “tetragonal” and non-superconducting orthorhombic Tl2Ba2Cu1O6

✍ Scribed by E.A. Hewat; P. Bordet; J.J. Capponi; C. Chaillout; J. Chenavas; M. Godinho; A.W. Hewat; J.L. Hodeau; M. Marezio

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 793 KB
• Volume: 156
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(88)90761-7

✦ Synopsis

HREM of samples of orthorhombic, non-superconducting T12Ba2CuIO6 and "tetragonal" superconducting TI2Ba2CuIO6 shows that the difference in orthorhombicity is associated with the degree of order of the superstructure. The superstructure modulation is unidirectional and is generated by the vector q= +0.07, 0.22, 1. This is not a principal direction of the sublattice. Twinning of the basic structure and superstructure results in small domains with eight different orientations. Since neutron diffraction shows that one in eight TI and O atoms are missing in the TIO bilayers, a model is proposed for the superstructure with one in eight T1 and O vacancies aligned along [ _+ 130 ] directions as required by the HREM images.