Electrochemical preparation and structural characterization of La[sub 2]NiO[sub 4+[delta]] phases (0 [le] [delta] [le] 0. 25)

Journal Article · Sun Aug 01 04:00:00 EDT 1993 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1993.1238· OSTI ID:7072192

Demourgues, A; Wattiaux, A; Grenier, J C; Pouchard, M; Soubeyroux, J L; Dance, J M; Hagenmuller, P ^[1]

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1. Laboratoire de Chimie, CNRS (France)

Electrochemical oxidation in alkaline solution has been used to control and to extend the oxygen overstoichiometry of La[sub 2]NiO[sub 4+[delta]] phases (0 [le] [delta] [le] 0.25). Chemical analysis has been carried out to determine the nickel (III) content and the related oxygen excess. Structural data (X-ray powder diffraction on La[sub 2]NiO[sub 4+[delta]] and neutron powder diffraction on La[sub 2]NiO[sub 4.25]) show that the interstitial oxygen atoms are introduced into the La[sub 2]O[sub 2] layers. ESR spectra for the La[sub 2]NiO[sub 4.25] compound recorded at 4.2 and 298 K characterize either low spin Ni[sup 3+] (t[sup 6][sub 2g]d[sup 1][sub x][sup 2][sub [minus]y][sup 2]) in a flattened octahedral site or Ni[sup +] (t[sup 6][sub 2g]d[sup 2][sub x][sup 2]d[sup 1][sub x][sup 2][sub [minus]y][sup 2]) in an elongated octahedron. The results show that the relaxation of the structure as a function of [delta] could arise either from a steric effect (i.e., formation of Ni[sup 3+]) or from a disproportionation of Ni[sup 2+] into Ni[sup +].

• OSTI ID: 7072192
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 105:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
COHERENT SCATTERING
DIFFRACTION
ELECTROCHEMISTRY
ELECTRON SPIN RESONANCE
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MAGNETIC RESONANCE
NEUTRON DIFFRACTION
NICKEL COMPOUNDS
NICKEL OXIDES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
RARE EARTH COMPOUNDS
REDUCTION
RESONANCE
SCATTERING
STOICHIOMETRY
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION