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The substitution of CO[sub 3] groups for copper in Y[sub 1[minus]x]Ca[sub x]Ba[sub 2]Cu[sub 3]O[sub 7]: HREM study

Journal Article · · Journal of Solid State Chemistry; (United States)
OSTI ID:5047859
The carbonation of the 123-type cuprates (Y[sub 1[minus]x]Ca[sub x])[sub n]Ba[sub 2n]Cu[sub 3n[minus]1]CO[sub 3]O[sub 7n[minus]3] has been studied by high-resolution electron microscopy. The investigation of the system, varying x and n, shows that the most stable phase is the n = 2 member. A structural model is proposed from XRD profile analysis for Y[sub 1.3]Ca[sub 0.7]Ba[sub 4]Cu[sub 5]CO[sub 3]O[sub 11]. The contrast of the HREM images was calculated on the basis of the XRD data and is discussed depending on focus values, carbon substitution, and crystal thickness. The study of the distribution of the CO[sub 3] groups versus composition shows that different n members are locally stabilized, from n = 1 to n = [infinity]. Short thermal treatments involve the formation of local ordering, in domains of some tens of angstroms width, which correspond to local superstructures along [110] and [031]; 90[degrees] oriented domains are frequent phenomena in these materials, and the boundaries are generally parallel to (001). Some intergrowth defects, in the form of [open quotes]124[close quotes] members, are observed.
OSTI ID:
5047859
Journal Information:
Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 108:2; ISSN 0022-4596; ISSN JSSCBI
Country of Publication:
United States
Language:
English