The effect of Ca doping on the structures of YBa[sub 2]Cu[sub 4]O[sub 8] and Y[sub 2]Ba[sub 4]Cu[sub 7]O[sub 14+x] single crystals

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1994.1203· OSTI ID:6836972

Schwer, H; Kaldis, E; Karpinski, J ^[1]; Rossel, C ^[2]

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1. Laboratorium fuer Festkoerperphysik, Zuerich (Switzerland)
2. Zurich Research Lab., Rueschlikon (Switzerland)

The transition temperature of YBa[sub 2]Cu[sub 4]O[sub 8] (124) is increased by about 10 K by doping with calcium, whereas Ca substitution in Y[sub 2]Ba[sub 4]Cu[sub 7]O[sub 14+x] (247) has no effect on [Tc]. X-ray structure refinements of 13 YBa[sub 2]Cu[sub 4]O[sub 8] and 12 Y[sub 2]Ba[sub 4]Cu[sub 7]O[sub 14+x] Ca-doped and undoped single crystals have been performed in order to determine structural changes due to Ca doping. In 124 a major fraction of Ca replaces Y; in 247 Ba1 (single-chain 123 unit) and Y are substituted by Ca in the ratio 3:2. The changes of the charge distribution caused by the substitution of trivalent Y[sup 3+] by divalent Ca[sup 2+] and ion size effects lead to structural changes in Ca-doped crystals. One structural consequence of the replacement of the small Y (r = 1.02 [angstrom]) by the larger Ca (r = 1.12 [angstrom]) is the increase of the distance between the adjacent oxygen planes in the c direction. In 247 the 123 unit is compressed due to the substitution of Ba1 by the smaller Ca. Ca doping diminishes the buckling of the CuO[sub 2] superconducting layers. The Ba-O sublattices in the double-chain 124 units of 247 and 124 are identical and change in the same way upon Ca doping; differences are observed in the Ba-Y sublattice.

• OSTI ID: 6836972
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 111:1; ISSN 0022-4596; ISSN JSSCBI
• 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
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
CRYSTAL DOPING
CRYSTAL STRUCTURE
CRYSTALS
CUPRATES
DIFFRACTION
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
SCATTERING
STOICHIOMETRY
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
YTTRIUM COMPOUNDS