The Cuprate Bi6Ba4Cu2O15: A Double Collapsed 2201-Type Structure

✍ Scribed by M. Hervieu; C. Michel; M.T. Caldes; A.Q. Pham; B. Raveau

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 845 KB
• Volume: 107
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1329

✦ Synopsis

A new cuprate, (\mathrm{Bi}{6} \mathrm{Ba}{4} \mathrm{Cu}{2} \mathrm{O}{15}), with a monoclinic symmetry ((a=12.191 \AA), (b=5.555 \AA, c=27.00) (\AA ; \beta=93.31^{\circ}) has been isolated. The high-resolution electron microscopy study of this phase has allowed a structural model to be established. The structure is deduced from that of the 2201 -modulated superconductor by a double "collapsing operation," and is called for this reason "double collapsed 2201-type" structure. Indeed, a first translation along (c_{2201}) of (a_{\mathrm{p}}(1+\sqrt{2} / 2)), every five octahedral block leads to the hypothetical (n=5)-member of the collapsed family (\left(a_{\mathrm{p}}\right.) is the parameter of the ideal cubic cell of the perovskite); a second translation performed in the latter structure along (\mathbf{b}{2201}) of (a{\mathrm{p}} \sqrt{2}) leads to the present structure. In fact, this structure consists of " 2201 "'-type slices, parallel to (012) ({ }{2201}), whereas the (n=5) collapsed structure would consist of identical slices but parallel to ((010){2201}). The analogy of these crystallographic collapsed structures with the crystallographic shear structures suggests the existence of two families of structures characterized by two kinds of crystallographic collapsing planes (CCP), ({010}{2201}) and ({012}{2291}), respectively. The oxides (\mathrm{Bi}{17} \mathrm{Sr}{16} \mathrm{Cu}{7} \mathrm{O}{49,8}) and (\mathrm{Bi}{15}(\mathrm{Sr}), Ba) ({ }{14} \mathrm{Cu}{6} \mathrm{O}{42}) represent the members (n=8) and 7 of the first family called collapsed, whereas the cuprate (\mathrm{Bi}{6} \mathrm{Ba}{4} \mathrm{Cu}{2} \mathrm{O}{15}) represents the member (n=5) of the second family called 2201-type double collapsed. O 1993 Academic Press, Inc.