Oxidation and reduction of BaLa sub 4 Cu sub 5 O sub 13+. delta

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Journal of Solid State Chemistry; (USA)

DOI:https://doi.org/10.1016/0022-4596(90)90231-L· OSTI ID:6085236

Davies, P K; Katzan, C M ^[1]

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1. Univ. of Pennsylvania, Philadelphia (USA)

The stability of the metallic, nonsuperconducting cuprate, BaLa{sub 4}Cu{sub 5}O{sub 13+{delta}}, was investigated using thermogravimetric analysis and X-ray and electron diffraction. In air or oxygen this highly oxidized compound only loses small amounts of oxygen; and at 1,000{degree}C the formal copper valence is close to 2.3{sup +}. To probe the chemical and structural factors that stabilize this high valence state, methods were developed to reduce the 145 structure. Under helium gas a new structure with {delta} {approx} {minus}0.5 was obtained; however, the removal of additional oxygen could only be accomplished by reducing the samples at low temperatures under 15% H{sub 2}/85% Ar gases. Under these conditions two additional structures were isolated for phases with {delta} {approx} {minus}1.0 and {minus}2.0. The differences in the x-ray patterns of these new phases result from a change in the symmetry of the perovskite subcell from cubic to orthorhombic to tetragonal. Models for the reaction sequence involved a systematic reduction in the coordination of the octahedral Cu groups in the oxidized structure to square pyramidal, square planar, and finally linear coordination in the fully reduced samples.

• OSTI ID: 6085236
• Journal Information: Journal of Solid State Chemistry; (USA), Journal Name: Journal of Solid State Chemistry; (USA) Vol. 88:2; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COHERENT SCATTERING
COPPER COMPOUNDS
CUPRATES
DATA
DIFFRACTION
ELECTRON DIFFRACTION
EXPERIMENTAL DATA
GRAVIMETRIC ANALYSIS
INFORMATION
LANTHANUM COMPOUNDS
NUMERICAL DATA
OXIDATION
OXYGEN COMPOUNDS
PHASE STUDIES
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTH COMPOUNDS
REDUCTION
SCATTERING
STRUCTURAL CHEMICAL ANALYSIS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION