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 00:00:00 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]

---

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), Vol. 105:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

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