Neutron diffraction studies of stoichiometric and oxygen intercalated La2NiO4 single crystals

Paulus, Werner; Cousson, A.; Dhalenne, G.; Berthon, J.; Revcolevschi, A.; Hosoya, Shoichi; Treutmann, W.; Heger, G.; Toquin, Ronan Le

doi:10.1016/s1293-2558(02)01299-2

Cited by 73 publications

(66 citation statements)

References 36 publications

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“…The rocking curve of, for example, the (400) reflection indicates a FWHM of the as-grown CFO crystals to be on the order of 0.2°. The ω-scans for the (hh0) reflections (i.e., the (−2-20) and the equivalent (−220) reflections) show unique reflections, confirming that no twinning as discussed in [30] occurred during crystal growth. The absence of twinning in nearly all batches we carried out can also be interpreted as evidence of the absence of a cubic perovskite modification, at least up to the melting temperature of Ca2Fe2O5, which is around 1350 °C.…”

Section: Ca 2 Fe 2 Osupporting

confidence: 64%

“…The rocking curve of, for example, the (400) reflection indicates a FWHM of the as-grown CFO crystals to be on the order of 0.2 • . The ω-scans for the (hh0) reflections (i.e., the (−2-20) and the equivalent (−220) reflections) show unique reflections, confirming that no twinning as discussed in [30] occurred during crystal growth. The absence of twinning in nearly all batches we carried out can also be interpreted as evidence of the absence of a cubic perovskite modification, at least up to the melting temperature of Ca 2 Fe 2 O 5 , which is around 1350 • C. In the case of the presence of a cubic parent phase, one would expect the formation of twin domains, as is the case for Sr 2 Fe 2 O 5 [16]; instead, the as-grown crystals do not show any observable macroscopic twin domains, but uniformly-shaped crystal ingot.…”

Section: Ca 2 Fe 2 Osupporting

confidence: 64%

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Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

2016

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High quality stoichiometric brownmillerite-type oxide single crystals have been successfully grown by the floating zone method using a mirror furnace. We report here on the growth conditions and structural characterization of two model compounds: Ca 2 Fe 2 O 5 and Sr 2 ScGaO 5 . Both show oxygen deficiency with respect to the average perovskite structure, and are promising candidates for oxygen ion conductivity at moderate temperatures. While Sr 2 ScGaO 5 single crystals were obtained in the cubic oxygen-deficient perovskite structure, Ca 2 Fe 2 O 5 crystallizes in the brownmillerite framework. Having no cubic parent high temperature counterpart, Ca 2 Fe 2 O 5 crystals were found to be not twinned. We report on structural characterization of the as-grown single crystals by neutron and X-ray diffraction, as well as scanning electron microscopy (SEM) coupled with EDX (Energy Dispersive X-Ray Spectroscopy) analysis and isotope exchange experiments.

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Section: Ca 2 Fe 2 Osupporting

confidence: 64%

Section: Ca 2 Fe 2 Osupporting

confidence: 64%

Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

2016

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“…The oxygen molecular adsorption and dissociation on the surfaces are also mediated by the oxygen vacancies. Unlike these conventional materials, in RP oxides the oxygen species intercalate through interstitial positions on the surface (12). Moreover according to theoretical calculations, the oxygen diffusion coefficient in the RP oxides increases with increase in oxygen over-stoichiometry up to a certain level (13).…”

Section: Introductionmentioning

confidence: 95%

Surface Chemistry and Non-Stoichiometry of Nd₂NiO₄₊ _δ Epitaxial Thin Films with Different Orientation and Strain

Цветков

Chen

et al. 2013

ECS Trans.

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(001)-oriented films with tensile and compressive lattice strain along c-axis were fabricated using pulsed laser deposition method. A significant decrease in the c-lattice parameter during annealing was found by x-ray diffraction (XRD) for the tensile strained films. X-ray photoelectron spectroscopy (XPS) showed that Ni reduction during annealing takes place only in compressively strained films, indicating the lower content of oxygen interstitials. A lower interstitial content in the compressively strained NNO films is consistent with the smaller c-lattice parameter measured by XRD and the easier reducibility of Ni measured by XPS. Cation segregation and morphological changes were found only for the compressively strained film surfaces. These results show that lattice strain along the c-axis is an important parameter that can alter the surface chemistry, and thus the oxygen exchange kinetics, on Nd 2 NiO 4+δ at elevated temperatures.

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“…Atomistic simulations have indicated that the incorporated oxygen excess is charge compensated by creation of nickel holes 12,13 whereby the oxygen interstitial concentration is accommodated by the presence of Ni 2+ /Ni 3+ . The ideal A 2 BO 4 structure is tetragonal, however the addition of oxygen interstitials leads to distortion from the ideal structure and is accommodated by tilting of the NiO 6 octahedra, which leads to an orthorhombic structure 14,15 .…”

Section: Introductionmentioning

confidence: 99%

In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes

et al. 2012

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The phase stability and compatibility of intermediate temperature solid oxide fuel cell (IT-SOFC) composite cathodes of lanthanum nickelate, La 2 NiO 4+δ (LNO), and ceria-gadolinium oxide, Ce 0.9 Gd 0.1 O 2-δ (CGO10), have been investigated by high resolution synchrotron X-ray diffraction (XRD). No reaction was observed between LNO and CGO10 at temperatures of up to 900°C when the composite is open to an ambient air environment. However, in a sealed capillary environment the 50:50 wt% LNO:CGO10 composite undergoes a partially reversible reaction at temperatures of 750°C and above, whereby LNO decomposes to La 2 O 3 and Ni. Changes in the CGO10 Bragg peaks indicate that this component is actively involved in this process. This study shows that the phase stability of LNO:CGO10 composites is highly dependent on oxygen partial pressure. In addition, it is observed that ex-situ XRD is insufficient to determine the presence of reactivity in composite cathodes and that high resolution in-situ XRD measurements are required to obtain details of the complexity of phase stability in SOFC composite cathodes. Figure 1 oriented with the b axis in the long direction; a slight tilting of the nickel octahedra can be seen in the Bmab structure shown in Figure 1(a). From the studies discussed above 7, 18-21 it appears that LNO reacts with fluorite structured ceria based electrolytes and is apparently stable in contact with perovskite-type lanthanum gallate. However, all of these studies were performed using ex-situ XRD, that is, XRD was performed at room temperature after the composite had been annealed. With this method it is not possible to monitor any reactions as they develop, as either a function of temperature or time, nor is it possible to identify whether there is any degree of reversibility. This study differs from those previously undertaken through the use of in-situ synchrotron XRD, enabling a detailed probing of the reaction mechanisms as a function of temperature, time and environment. Whilst it is apparent from the ex-situ XRD studies, that there is ready formation of higher order Ruddlesden-Popper phases under certain conditions, it is likely that LNO phase stability is sensitive to oxygen partial pressure and temperature and there is a need to 5 investigate the reaction as it develops; for this reason, we have undertaken in-situ studies of LNO:CGO10 composites using high resolution synchrotron X-ray powder diffraction. ExperimentalA 50:50 wt% composite of LNO:CGO10 was created from LNO powder (Cerpotech) and CGO10 powder (Praxair), which were calcined separately at 1400°C for 5 hours. The relative weight percentage of each powder was measured for the desired composition and the mixture was ballmilled with zirconia mixing balls for 24 hours in ethanol. The resultant composite powder was dried at 100°C for 16 hours. All synchrotron X-ray diffraction patterns were obtained on beamline I11 at the Diamond Light Source, UK. Technical descriptions of the I11 instrument can be found in the paper by Thompson et...

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Neutron diffraction studies of stoichiometric and oxygen intercalated La2NiO4 single crystals

Cited by 73 publications

References 36 publications

Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

Surface Chemistry and Non-Stoichiometry of Nd₂NiO₄₊ _δ Epitaxial Thin Films with Different Orientation and Strain

In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes

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Neutron diffraction studies of stoichiometric and oxygen intercalated La2NiO4 single crystals

Cited by 73 publications

References 36 publications

Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

Influence of Phase Transformations on Crystal Growth of Stoichiometric Brownmillerite Oxides: Sr2ScGaO5 and Ca2Fe2O5

Surface Chemistry and Non-Stoichiometry of Nd2NiO4+ δ Epitaxial Thin Films with Different Orientation and Strain

In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes

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Surface Chemistry and Non-Stoichiometry of Nd₂NiO₄₊ _δ Epitaxial Thin Films with Different Orientation and Strain