The effect of thallium and oxygen stoichiometry on structure and [Tc] in Tl-2201 and Tl-2212

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

DOI:https://doi.org/10.1006/jssc.1994.1110· OSTI ID:7016727

Stroem, C; Eriksson, S G; Johansson, L G ^[1]; Simon, A; Mattausch, H J; Kremer, R K ^[2]

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1. Chalmers Univ. of Technology and Univ. of Goeteborg, Goeteborg (Sweden)
2. Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

By a novel method the authors have prepared the high-Tc superconductors Tl[sub 2[minus]x]Ba[sub 2]CuO[sub 6[minus]d] (Tl-2201) and Tl[sub 2[minus]x]Ba[sub 2]CaCu[sub 2]O[sub 8[minus]d] (Tl-2212) in a reproducible way with respect to purity, thallium and oxygen content, crystal structure, and superconducting properties. The changes in structure induced by changes in thallium or oxygen content were studied by X-ray and neutron powder diffraction techniques. Tl-2201 crystallizes in either the tetragonal or orthorhombic system, and both forms can be made superconducting. The detailed atomic order in the Tl[sub 2]O[sub 4] layers seems to be determined by the thallium as well as by the oxygen content. A high thallium and oxygen content stabilizes the orthorhombic form. Tl-2212 has tetragonal symmetry irrespective of thallium or oxygen content. In samples low in thallium content no single layer thallium compounds are formed, the thallium deficiency being accommodated as statistically distributed vacancies in the Tl[sub 2]O[sub 4] layers. The oxygen content is the main factor in determining Tc in Tl-2201 and Tl-2212. Low thallium content promotes higher Tc's, whereas addition of oxygen to the as-prepared samples decreases Tc. The c-axis length and the atom displacements, in particular in the Tl-2212 system, can be explained in terms of a charge redistribution as for the Y-123 system. An increase in oxygen content leads to a shift of Ba[sup 2+] toward the Tl[sub 2]O[sub 4] layers, and to an increase in the CuO[sub 2] plane puckering as expected from an increase in hole concentration in the CuO[sub 2] planes.

• OSTI ID: 7016727
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 109:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360607* -- Other Materials-- Superconducting Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
HIGH-TC SUPERCONDUCTORS
NEUTRON DIFFRACTION
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
STOICHIOMETRY
SUPERCONDUCTORS
TETRAGONAL LATTICES
THALLIUM COMPOUNDS
THALLIUM OXIDES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
X-RAY DIFFRACTION