Valence state for bismuth in the superconducting bismuth cuprates

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.193· OSTI ID:6910346

Retoux, R; Studer, F; Michel, C; Raveau, B ^[1]; Fontaine, A; Dartyge, E ^[2]

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1. CRISMAT, Institut des Sciences de la Matiere et du Rayonnement, 14032 Caen CEDEX, (France)
2. Laboratoire pour l'Utilisation du Rayonnement Electromagnetique, Centre National de la Recherche Scientifique MEN, Comissariat a la Energie Atomique, 91405 Orsay CEDEX, (France)

X-ray-absorption near-edge spectra (XANES) of high-{ital T}{sub {ital c}} bismuth superconductors (2:2:0:1, 2:2:1:2, and 2:2:2:3) have been recorded at the Bi {ital L}{sub III}, {ital L}{sub I}, and Cu {ital K} edges. With respect to the reference Bi{sub 2}O{sub 3} (Bi(III) valence state), edge shifts towards low energies have been found in the spectra of all the superconducting cuprates at the Bi {ital L}{sub III} edge. This has been interpreted in terms of a reduced bismuth valency smaller than Bi (III). This result is a characteristic of the superconducting intergrowths, since other layer compounds with Bi cations in similar environments, Bi{sub 2}SrNb{sub 2}O{sub 9} and Bi{sub 2}Sr{sub 2}CaFe{sub 2}O{sub 9}, do not present any shift with respect to Bi{sub 2}O{sub 3}. The copper formal valency has been deduced either from charge-balance considerations assuming a well-known oxygen stoichiometry or edge shifts at the copper {ital K} edge. High copper valencies have been found, especially in the 2:2:0:1 compound, but again, as was observed before in thallium and lead-substituted thallium cuprates, critical temperatures increase when the copper valency decreases, i.e., when the number of holes per copper in an oxygen-like {ital p} band decreases, provided this number stands above a critical value estimated previously to be 0.17.

• OSTI ID: 6910346
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:1; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTRA
ALKALINE EARTH METAL COMPOUNDS
BISMUTH
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
LEAD COMPOUNDS
LEAD OXIDES
METALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
SPECTRA
STOICHIOMETRY
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VALENCE
X-RAY DIFFRACTION
X-RAY SPECTRA