An X-ray diffraction study of the oxygen content phase diagram of La[sub 2]NiO[sub 4+[delta]]

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

DOI:https://doi.org/10.1006/jssc.1993.1208· OSTI ID:5841894

Rice, D E; Buttrey, D J ^[1]

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1. Univ. of Delaware, Newark (United States)

The oxygen concentration phase diagram of La[sub 2]NiO[sub 4+[delta]] has been constructed from room temperature X-ray powder diffraction data on specimens spanning a wide range of oxygen stoichiometries. Contrary to some previous reports, the authors find multiple biphasic regions. The most stoichiometric phase ([delta] [approx] 0.00) is orthorhombic with Bmab (low temperature orthorhombic, LTO) symmetry in agreement with previous studies. A new distorted tetragonal phase with P4[sub 2]/ncm (low temperature tetragonal, LTT) symmetry is observed for oxygen excess levels in the range 0.020 < [delta] < 0.030. Undistorted tetragonal (high temperature tetragonal, HTT) symmetry is observed for oxygen compositions from [delta] [approx] 0.055 to at least [delta] = 0.137. An orthorhombic phase appears for [delta] [approx] 0.168. The temperature dependence of the reduction boundary has been determined; however, in contrast with the Pr[sub 2]NiO[sub 4+[delta]] system, no evidence of the oxidation boundary has been observed. The room temperature LTT phase is consistent with lower temperature observations of weak ferromagnetism associated with spin canting. 24 refs., 7 figs., 1 tab.

• OSTI ID: 5841894
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 105:1; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
&amp; Refractories-- Structure &amp; Phase Studies
ANGULAR MOMENTUM
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIAGRAMS
DIFFRACTION
FERROMAGNETISM
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MAGNETISM
NICKEL COMPOUNDS
NICKEL OXIDES
ORTHORHOMBIC LATTICES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PARTICLE PROPERTIES
PHASE DIAGRAMS
PHASE STUDIES
RARE EARTH COMPOUNDS
REDUCTION
SCATTERING
SPIN
STOICHIOMETRY
SYMMETRY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION