F-K XANES Studies of Alkaline-Earth Fluorides

Oizumi, Hiroaki; Fujikawa, Takashi; Ohashi, Masanao; Maezawa, H.; Nakai, S.

doi:10.1143/jpsj.54.4027

Cited by 33 publications

(16 citation statements)

References 23 publications

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“…These observed spectra showed similar spectral profiles as earlier experiments. 12,14) The most intense peak, peak E, appeared at the threshold, 687.8 eV, in the case of ZnF 2 , while only weak peak, peak A, was shown there and second peak, peak B, was the most intense one in the spectrum of MgF 2 . In order to interpret these differences in observed NEXAFS spectra between MgF 2 and ZnF 2 , we performed the first principles DFT calculations.…”

Section: Resultsmentioning

confidence: 94%

“…[2][3][4][5][6][7] The NEXAFS spectra at F K-edge were extensively studied both experimentally and theoretically for alkali fluorides, [8][9][10][11] and alkaline-earth difluorides. 12,13) Those of the 3d transition metal difluorides with the rutile type of structure have been also investigated. [14][15][16][17] However their theoretical calculations have provided only qualitative reproductions of the experimental data.…”

Section: Introductionmentioning

confidence: 99%

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First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF2 and ZnF2

et al. 2004

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First principles calculations have been carried out to investigate the core-hole effects on the theoretical fine structures of the X-ray absorption spectra of MgF 2 and ZnF 2 at F K-edge. Significant differences are found between the calculated spectral fine structures with and without core-holes. Experimental profiles of the near-edge X-ray absorption fine structures are well reproduced by the theoretical ones when the core-hole effect is introduced. The dependence of supercell size on the theoretical fine structures is also examined.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF2 and ZnF2

et al. 2004

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“…We were interested in determining whether the near edge structure could be used to determine ionicity as reported by Oizumi et al (1985) [7] in a study in alkali halides. We applied the XANES method to the calculation of the near edge structure on the oxygen K edge of various oxides with the NaCI structure (see Fig.…”

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confidence: 99%

The interpretation of near edge structure

Rez

Weng

1991

Microsc. Microanal. Microstruct.

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Abstract. 2014 The near edge structure up to 30 eV above the ionisation threshold of inner shell edges can be interpreted either as the result of interference of waves scattered from neighbouring atoms or in terms of the local projected conduction band density of states. Methods of calculating near edge structure based on both these viewpoints will be discussed and applications to the near edge structures observed in semiconductors and insulators reviewed. Particular emphasis will be given to those cases where the calculations lead to a simple interpretation of near edge structure.The characteristic inner shell edges observed in electron energy loss spectroscopy have traditionally been used for elemental analysis. Now that spectrometers capable of giving about 1 to 1.5 eV resolution on conventional TEMs and 0.3 to 0.5 eV resolution on cold field emission STEMs have become available the observation of fine structure oscillations has become routine.In particular the large modulations within the first 20 to 30 eV above threshold have become easy to observe and can be detected even when the element is present in low concentrations (below about 10% relative to the majority constituent). It would be advantageous if the fine structures could give some new information on the microstructure of the material, especially if that information could not be obtained in other ways. The materials scientist would like to know whether the near edge structure gives information about elemental charge state, local bonding or the local nature of the conduction band. Alternatively the fine structure might be sensitive to environment or coordination number. Another possibility is that it only reflects interatomic bond distances, but in a more convoluted way than the much weaker extended fine structure which starts about 30eV above threshold.One approach to understanding near edge structure is to collect "fingerprints" from elements in similar environments and try to identify common features (see the article by Brydson in this volume). The other approach, which is adopted in this paper, is to calculate the near edge structure using appropriate theory and identify those features which show sensitivity to a property of interest. In practice both methods can be valuable and they readily complement each other.Calculations have traditionally relied on two theoretical approaches. The most common method, which has been extensively used by the X-ray absorption community, is the cluster calculation or XANES method of Durham et al. (1982) [1]. The key idea is that the fine structure Article available at

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“…XAS at La 3d and F 1s edges was acquired in TEY mode, by measuring the drain current from the samples, and in FY mode, using a Vacuum Silicon Drift Spectrometer by PN Detector GmbH and XGlab electronics. The photon energy was calibrated using the known position of 688.6 eV of the first narrow peak in the F 1s absorption spectrum of SrF 2 …”

Section: Methodsmentioning

confidence: 99%

Buried Interfaces Effects in Ionic Conductive LaF₃–SrF₂ Multilayers

Koshmak

Banshchikov

Ciancio

et al. 2017

Adv Materials Inter

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Solid-state materials that express enhanced ionic transport properties at the nanoscale attract an increasing interest.In multiphase/multilayer solid electrolytes, the composition, reactivity, and structure of interfaces between materials and phases play a fundamental role for fast ion-conduction. Here, the properties of buried interfaces in prototypical fast ion-conducting LaF 3 /SrF 2 epitaxial multilayers are investigated. Photoelectron spectroscopy-both with soft-X and high-energy photons-is applied to separate composition and reactivity of buried interfaces with respect to the outermost surface. X-ray reflectivity, high-energy electron diffraction, X-ray diffraction, atomic force and transmission electron microscopies are used to study morphology, layer crystallinity, epitaxy relations, and buried interface structure. It is found that while the alternated layers present good crystallinity and high lattice matching, with formation of almost ideal sharp interfaces, buried interfaces show a sizeable reduction of the energy barrier for F vacancy formation with respect to bare materials. A density higher by a factor of six of fluorine vacancies is observed at buried interfaces in multilayers with respect to the bare materials. This is correlated to the formation of space charge regions, favoring ion conduction. The formation of F depleted La fluoride regions at interfaces is also promoted by annealing. This is associated to the increase of ion conductivity in annealed heterostructures reported in literature.Applications span from energy and data storage in miniaturized systems to sensoristics. [1][2][3][4] Enhancement of conductivity by several orders of magnitude has been observed in epitaxial multilayer structures [5][6][7] and ascribed to interfacerelated nanoscale effects. Crystal structure, defects, chemical composition, and electronic band structure of interfaces between ionic conductors in a multiphase system, like a multilayer, are crucial aspects to consider in order to understand, and to control, the ionic conduction phenomena.Here we focus our attention on the chemical reactivity at interfaces between materials with different (ion) conducting properties. For this purpose, heterostructures based on alternate layers of LaF 3 and SrF 2 have been chosen.Fluorides represent prototypical systems. Their simple crystal structure makes them ideal for fundamental studies on the conduction mechanisms. Good ionic conductors such as LaF 3 are highly responsive toward irradiation and temperature modifications [8] which can be explained by high mobility of the lattice ions. Multilayer/ multiphase materials based on LaF 3 further foster the ionic

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F-K XANES Studies of Alkaline-Earth Fluorides

Cited by 33 publications

References 23 publications

First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF<SUB>2</SUB> and ZnF<SUB>2</SUB>

First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF<SUB>2</SUB> and ZnF<SUB>2</SUB>

The interpretation of near edge structure

Buried Interfaces Effects in Ionic Conductive LaF₃–SrF₂ Multilayers

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F-K XANES Studies of Alkaline-Earth Fluorides

Cited by 33 publications

References 23 publications

First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF<SUB>2</SUB> and ZnF<SUB>2</SUB>

First Principles Study of Core-hole Effect on Fluorine K-edge X-ray Absorption Spectra of MgF<SUB>2</SUB> and ZnF<SUB>2</SUB>

The interpretation of near edge structure

Buried Interfaces Effects in Ionic Conductive LaF3–SrF2 Multilayers

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Resources

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Buried Interfaces Effects in Ionic Conductive LaF₃–SrF₂ Multilayers