LaSrCrxNi1-xO4+δ:  Crystal Chemistry, Magnetism, and the Stabilization of NiI in an Oxide Environment

Millburn, J. E.; Rosseinsky, M. J.

doi:10.1021/cm960357v

Cited by 20 publications

(13 citation statements)

References 38 publications

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“…The conditions in our in situ reduction experiment were clearly not strong enough to induce a mean oxidation state below 2.0, as has been seen previously in the x ¼ 0.0 compound 17 and reported in Ni-based related systems. [31][32][33] The ADPs after reduction, both at 600 C and on cooling to 57 C, show the same anisotropy as was observed in the composition x ¼ 0.0 and are again indicative of rotations of the reduced anion polyhedra. The observed range of oxygen stoichiometries corresponds to the presence of both 6and 5-fold coordination polyhedra, the latter varying from 20 to 40% within the regime where rotation seems likely.…”

Section: Discussionsupporting

confidence: 62%

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

et al. 2011

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International audienceNeutron powder diffraction has been used to investigate the redox behaviour of two n = 1 Ruddlesden-Popper (RP) oxides, La(1.5+x)Sr(0.5-x)Co(0.5)Ni(0.5)O(4+delta) (x = 0.0, 0.2) in situ and in real time during cycling through the temperature range 20 < T/degrees C < 600 under flowing 5% H(2). Both compositions retained I4/mmm symmetry throughout the heating and cooling cycle. Rietveld refinement of data collected at room temperature showed the presence of interstitial oxygen in the original samples (delta approximate to 0.06(1) and 0.12(1) for x 0.0 and 0.2, respectively). When heated in flowing H(2), both compositions were reduced over the temperature range 300 < T/degrees C < 600 (delta approximate to -0.22(2) and -0.06(2) for x 0.0 and 0.2, respectively). In the case of the x = 0.2 material, reduction clearly occurred first at the interstitial site (O(int)), then at the equatorial site (O(eq)). The changes in composition were accompanied by changes in unit-cell parameters and bond lengths. Rietveld refinements revealed residual partial occupation of the O(int) site in the reduced x = 0.2 sample. This is the first structural evidence of the coexistence of both anion vacancies and interstitial anions in a hypostoichiometric n = 1 RP oxide. The temperature dependence of the atomic displacement parameters is consistent with the presence of local rotations of the anion-deficient coordination polyhedra. On heating the reduced x = 0.2 material in an O(2) flow, the refilling of both the O(eq) and O(int) sites began at 200 degrees C and the stoichiometry of the original as-prepared sample was recovered by 250 degrees C

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Section: Discussionsupporting

confidence: 62%

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

et al. 2011

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“…[26]. The tendencies can be explained by the different ionic radii of the ions in sixfold coordination, which are 56, 54.5 and 64.5 pm [27] for Ni 3+ (low-spin) [28], Co 3+ (high-spin) [29,30] and Fe 3+ (high-spin) [31 ], respectively. In the series La(Ni 0.5 Fe 0.5 ) 1-x Co x O 3, a r decreases as the cobalt content increases because the ionic radius of Co 3+ is smaller than the average radius of Ni 3+ and Fe 3+ , whereas in the series LaNi 0.…”

Section: Chemical Analysis and Xrdmentioning

confidence: 99%

Material properties of perovskites in the quasi-ternary system LaFeO3–LaCoO3–LaNiO3

Tietz

Raj

et al. 2016

Journal of Solid State Chemistry

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An overview is presented on the variation of electrical conductivity, oxygen permeation, and thermal expansion coefficient as a function of the composition of perovskites in the quasiternary system LaFeO 3-LaCoO 3-LaNiO 3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni 0.5 Fe 0.5) 1-x Co x O 3 and LaNi 0.5-x Fe x Co 0.5 O 3 , are presented after the powders had been sintered at 1100°C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi 0.5 Fe 0.5 O 3 for which 60% rhombohedral and 40% orthorhombic phase was found. The maximum DC electrical conductivity value of the perovskites at 800 °C was 1229 S cm-1 for the composition LaCoO 3 and the minimum was 91 S cm-1 for the composition LaCo 0.5 Fe 0.5 O 3. The oxygen permeation of samples with promising conductivities at 800 °C was one order of magnitude lower than that of La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 °C was obtained with LaNi 0.5 Co 0.5 O 3. The coefficients of thermal expansion varied in the range of 13.2 × 10-6 K-1 and 21.9 × 10-6 K-1 for LaNi 0.5 Fe 0.5 O 3 and LaCoO 3 , respectively. 57 Fe Mössbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. The substitution had a great influence on the chemical properties of the materials.

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“…This behaviour, contrary to the Nd 2− x Ba x NiO 4+ δ cases (Takeda et al , 1992), may suggest an important role of hole trapping by the chrome cations forming stable Cr 3+ states. Such hypothesis seems well supported by numerous experimental data on the oxygen non-stoichiometry and phase stability of various LaSrCrO 4 -, LaSrNiO 4 -, LaSrCrO 3 - and LaSrNiO 3 -based solid solutions, which suggest a considerably higher stability of Cr 3+ compared to Ni 3+ (Sauvet and Irvine, 2004; Millburn and Rosseinsky, 1997).…”

Section: Resultsmentioning

confidence: 72%

Structural and electrical properties of Nd_1.7Ba_0.3Ni_0.9Cr_0.1O₄₊_δ compound

2012

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The Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ polycrystalline sample was synthesized by the sol-gel process and a subsequent annealing at 1523 K in 1 atm of flowing argon. X-ray diffraction (XRD) analysis and electrical transport properties have been investigated as well. The oxygen non-stoichiometry was determined by iodometric titration. The sample shows adoption of the K 2 NiF 4 -type structure based on a tolerance factor calculation. Rietveld refinement of the crystal structure from X-ray powder diffraction data confirmed that Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ adopts the tetragonal structure (space group I4/mmm, Z = 2). The room temperature unit-cell parameters are determined to be a = 3.82515(2) and c = 12.47528(6) Å. The reliability factors are: R B = 0.043, R wp = 0.012 and χ 2 = 3.00. The Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ compound exhibits a semi-conductive behaviour. The electrical transport mechanism has been investigated and it agrees with the adiabatic small polaron hopping model in the temperature range 313 K ≤ T ≤ 708 K.

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LaSrCr_xNi₁_-_xO₄₊_δ: Crystal Chemistry, Magnetism, and the Stabilization of Ni^I in an Oxide Environment

Cited by 20 publications

References 38 publications

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

Material properties of perovskites in the quasi-ternary system LaFeO3–LaCoO3–LaNiO3

Structural and electrical properties of Nd_1.7Ba_0.3Ni_0.9Cr_0.1O₄₊_δ compound

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LaSrCrxNi1-xO4+δ: Crystal Chemistry, Magnetism, and the Stabilization of NiI in an Oxide Environment

Cited by 20 publications

References 38 publications

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

High-temperature redox chemistry of La1.5+xSr0.5−xCo0.5Ni0.5O4+δ (x = 0.0, 0.2) studied in situ by neutron diffraction

Material properties of perovskites in the quasi-ternary system LaFeO3–LaCoO3–LaNiO3

Structural and electrical properties of Nd1.7Ba0.3Ni0.9Cr0.1O4+δ compound

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LaSrCr_xNi₁_-_xO₄₊_δ: Crystal Chemistry, Magnetism, and the Stabilization of Ni^I in an Oxide Environment

Structural and electrical properties of Nd_1.7Ba_0.3Ni_0.9Cr_0.1O₄₊_δ compound