New extended defects in the superconductive [open quotes]123[close quotes] oxycarbonitrate YCaBa[sub 4]Cu[sub 5](NO[sub 3])[sub x](CO[sub 3])[sub 1[minus]x]O[sub 11]: HREM study

Journal Article · Sun Aug 01 04:00:00 EDT 1993 · Chemistry of Materials; (United States)

DOI:https://doi.org/10.1021/cm00032a016· OSTI ID:7207492

Hervieu, M; Michel, C; Raveau, B ^[1]

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1. Universite de Caen, Boulevard du Marechal Juin (France)

A HREM study of the 72 K superconductor YCaBa[sub 4]Cu[sub 5](NO[sub 3])[sub x](CO[sub 3])[sub 1[minus]x]O[sub 11] has been performed. One observes, for many crystals, a very regular contrast characteristic of the [open quotes]2a[sub 123] x b[sub 123] x 2c[sub 123][close quotes] superstructure corresponding to an ordered stacking of the rows of CuO[sub 5] pyramids and of CO[sub 3] (NO[sub 3]) groups along [bar a], alternately. Contrary to YBa[sub 2]Cu[sub 3]O[sub 7], this compound does not exhibit any microtwinning in agreement with the pseudotetragonal character of its subcell. One observes three kinds of extended defects: (i) Intergrowths of other n members of the series (Y[sub 1[minus]x]Ca[sub x])[sub n]Ba[sub 2n]Cu[sub 3n[minus]1](NO[sub 3])[sub x](CO[sub 3])[sub 1[minus]x]O[sub 7n[minus]3], involving different local superstructures with a = 3a[sub 123], 4a[sub 123], and 6a[sub 123]; this suggests strongly the possibility to synthesize the members n = 3, 4, and 6. (ii) 90[degrees] oriented domains similar to those previously observed for [open quotes]123[close quotes] type oxycarbonates, whose junctions have been interpreted. (ii) Intergrowths of the [open quotes]123[close quotes] oxycarbonitrate and the Sr[sub 2]CuO[sub 2]CO[sub 3]-type structure. These defects are of capital important since they are the signature of the possible existence of a new series of oxycarbonates or nitrates, (Y[sub 1[minus]x]Ca[sub x])[sub 2]A[sub 2]Cu[sub 4]O[sub 9]-(A[sub 2]CuO[sub 2]MO[sub 3])[sub n] for A = Ba, Sr; M = C, N with an original structure and which might be superconductive. 10 figs.

• OSTI ID: 7207492
• Journal Information: Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 5:8; ISSN CMATEX; ISSN 0897-4756
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATES
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
HIGH-TC SUPERCONDUCTORS
MICROSCOPY
NITRATES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
STOICHIOMETRY
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS