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 00:00:00 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]

---

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), Vol. 111:1; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CRYSTAL STRUCTURE
CALCIUM OXIDES
CUPRATES
YTTRIUM COMPOUNDS
CRYSTAL DOPING
MONOCRYSTALS
STOICHIOMETRY
X-RAY DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
CRYSTALS
DIFFRACTION
OXIDES
OXYGEN COMPOUNDS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies