Synthesis, structure, and properties of the layered perovskite La[sub 3]Ni[sub 2]O[sub 7[minus][sigma]]
- State Univ. of New Jersey, Piscataway, NJ (United States) Univ. of Texas, Austin, TX (United States)
Single-phase samples of La[sub 3]Ni[sub 2]O[sub 7[minus][sigma]] with [sigma] = 0, 0.08, and 0.65 were prepared and characterized by powder X-ray diffraction, TGA, electrical resistivity, and magnetic susceptibility. The crystal symmetry of the as-prepared ([sigma] = 0.08) and oxygenated ([sigma] = 0.00) samples is orthorhombic (space group Fmmm). Oxidation of the as-prepared La[sub 3]Ni[sub 2]O[sub 6.92] sample to La[sub 3]Ni[sub 2]O[sub 7.00] shows little change in the unit-cell parameters. Reduction of La[sub 3]Ni[sub 2]O[sub 6.92] to La[sub 3]Ni[sub 2]O[sub 6.35] results in a structural phase transition from orthorhombic to tetragonal symmetry, a dramatic decrease in the c cell parameter, and significant increase in the a and b cell parameters. These data are consistent with loss of oxygen from the apical octahedral sites connecting two perovskite layers in La[sub 3]Ni[sub 2]O[sub 7[minus][sigma]]. The electrical transport properties change with decreasing oxygen content from metallic for La[sub 3]Ni[sub 2]O[sub 7.00] to semiconducting for La[sub 3]Ni[sub 2]O[sub 6.92] and La[sub 3]Ni[sub 2]O[sub 6.35]. The fully reduced sample, La[sub 3]Ni[sub 2]O[sub 6.35], shows a linear dependence of ln [rho] versus T[sup [minus]1/4] in the temperature range 90-140 K, suggesting a variable-range hopping mechanism. A nearly temperature-independent magnetic susceptibility is observed in the temperature range 100-300 K for the [sigma] = 0 and 0.08 samples. The relatively high values and the temperature dependence of the magnetic susceptibility indicate a Stoner enhanced Pauli paramagnetism for [sigma] = 0 and evidence for a weak ferromagnetism in the [sigma] = 0.65 sample. The electrical and magnetic properties of La[sub 3]Ni[sub 2]O[sub 7[minus][sigma]] are discussed in terms of the mixed-valent character of nickel and vacancy-induced localization effects.
- OSTI ID:
- 5114849
- Journal Information:
- Journal of Solid State Chemistry; (United States), Vol. 108:2; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LANTHANUM OXIDES
CRYSTAL STRUCTURE
PHYSICAL PROPERTIES
NICKEL OXIDES
ELECTRIC CONDUCTIVITY
LATTICE PARAMETERS
ORTHORHOMBIC LATTICES
PEROVSKITES
PHASE TRANSFORMATIONS
SEMICONDUCTOR MATERIALS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TETRAGONAL LATTICES
THERMAL GRAVIMETRIC ANALYSIS
CHALCOGENIDES
CHEMICAL ANALYSIS
CRYSTAL LATTICES
ELECTRICAL PROPERTIES
GRAVIMETRIC ANALYSIS
LANTHANUM COMPOUNDS
MATERIALS
NICKEL COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTH COMPOUNDS
TEMPERATURE RANGE
THERMAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties