On rare-earth clustering in flourite type solid solutions MF2REF3

Чернов, С. В.; Gunßer, W.; Murin, I. V.

doi:10.1016/0167-2738(91)90181-a

Cited by 14 publications

(10 citation statements)

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“…Hence, the microstructure seems to become more homogeneous. Furthermore, this means that for the sample with x = 0.75 clearly and solely showing the XRPD pattern of the fluorite structure an NMR line of considerable intensity representing fluoride ions in distorted F2/3 sites can be seen (see the two fit-lines in the spectra in Figure ), which is in agreement with the deliberations of Chernov et al and the results of Kadlec et al (see Section ). It should be kept in mind that the TEM micrographs as well as the XRPD patterns show no hints for noteworthy amounts of amorphous material.…”

Section: Results and Discussionsupporting

confidence: 90%

“…However, it should be noted that both structures should be highly distorted in this range of compositions as will be discussed later. Thus, one might assume that the samples with x = 0.80 and x = 0.85 may be transitional phases combining structural aspects of both structures and are not mixtures of differently structured crystallites of Ba 1−x La x F 2+x , which is essentially in agreement with the deliberations of Chernov et al 15 Figure 2, exhibit the average distances r of the ions in real space or, to be more exact, the probability to find ions in a certain distance from each other (by integration of G(r) from r 1 to r 2 ). 44 At first view the patterns of all the samples are very similar.…”

Section: Resultssupporting

confidence: 73%

“…However, a decrease of the ionic conductivity was not observed for monocrystalline Ba 1– x La x F 2+ x up to x ≈ 0.50. Kadlec et al assumed that this behavior may be explained by the assumption that the clusters formed are fragments of the tysonite structured fast fluoride ion conductor LaF 3 (see also ref ) such that networks of these clusters should also show a good ionic conductivity. As already mentioned, Andersen et al found evidence that at least some of the fluoride ions in the 2:2:2 clusters are mobile.…”

Section: Results and Discussionmentioning

confidence: 99%

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Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure

et al. 2014

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Ba 1−x La x F 2+x covering the whole range of compositions was synthesized by high-energy ball milling of mixtures of BaF 2 and LaF 3 at ambient temperature. The compounds obtained in this way crystallize in the cubic fluorite structure in the range from 0 ≤ x ≲ 0.775 which extends the range for the fluorite-type Ba 1−x La x F 2+x covered up to now (0 ≤ x ≤ 0.55) considerably. By employing 19 F NMR spectroscopy and X-ray (total) scattering, indications for a continuous change from the fluorite (BaF 2) to the tysonite structure (LaF 3) were found. The mechanosynthesized samples showed slightly higher fluoride ion conductivities for the samples with x ≤ 0.40 and clearly smaller conductivities in the case of the samples with x ≥ 0.85 than reported for their monocrystalline counterparts. Two conductivity maxima at x ≈ 0.40 and x ≈ 0.85 and a conductivity minimum at x ≈ 0.75 were observed for the mechanosynthesized Ba 1−x La x F 2+x. For the samples with 0.10 ≤ x ≤ 0.50, exhibiting a dc conductivity in the order of 10 −5 S/cm at 400 K, all fluoride ions seem to be highly mobile at temperatures beyond 453 K. The decrease of the ionic conductivity observed for Ba 1−x La x F 2+x with increasing x in the range from x ≈ 0.50 to x ≈ 0.75 is accompanied by a change of the diffusion behavior and a decrease of the ratio of highly mobile to nonmobile or slow fluoride ions.

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Section: Results and Discussionsupporting

confidence: 90%

Section: Resultssupporting

confidence: 73%

Section: Results and Discussionmentioning

confidence: 99%

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Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure

et al. 2014

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“…Близость" дефектных структур флюорита и тисонита [40,41,43], по-видимому, является причиной аддитивного закона изменения ионной проводимости (общего характера изменения lg σ dc ) в обоих типах нестехиометрических фаз с одинаковым качественным элементным составом в простых эвтектических системах SrF 2 −RF 3 (R = La−Nd).…”

Section: корреляция между величинами фтор-ионной проводимости нестехиunclassified

Корреляция между величинами фтор-ионной проводимости кристаллов Sr-=SUB=-1-x-=/SUB=-R-=SUB=-x-=/SUB=-F-=SUB=-2+x-=/SUB=- (тип CaF-=SUB=-2-=/SUB=-) и R-=SUB=-1-y-=/SUB=-Sr-=SUB=-y-=/SUB=-F-=SUB=-3-y-=/SUB=- (тип LaF-=SUB=-3-=/SUB=-) в системах SrF-=SUB=-2-=/SUB=--RF-=SUB=-3-=/SUB=- (R=La-Nd)

Сорокин¹,

Соболев²

2019

Физика Твердого Тела

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The “conductivity logarithm–composition” correlation logσ_dc( x ) = ax + b has been revealed for the strongly nonstoichiometric fluorite Sr_1 – _ x R_ x F_2 + _ x ( x is the RF_3 molar fraction, 0.15 ≤ x ≤ 0.47) and tysonite R_1 – _ y Sr_ y F_3 – _ y ( y is the SrF_2 molar fraction, y = 1 – x , 0.85 ≤ x ≤ 0.97) phases in the SrF_2–RF_3 systems (R = La, Ce, Pr, Nd). The conductivity σ_dc of the eutectic 70LaF_3 + 30SrF_2 (mol %) composite fits well with the dependence logσ_dc( x ) for the nonstoichiometric Sr_1 – _ x La_ x F_2 + _ x and La_1 – _ y Sr_ y F_3 – _ y phases.

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“…2 If several structural modifications of the compound can occur, the impurity atoms tend to give rise to the coordination typical of the modification that is the nearest to the phase of the host crystal in the phase diagram. 24 The possibility of the presence of statistically distributed cluster groups in the structure of a solid solution is often evidenced by unreasonably shortened interatomic distances.…”

Section: Short-range Ordermentioning

confidence: 99%

Crystal structures of inorganic compounds with atomic defects

Frank-Kamenetskaya¹

2003

Russ. Chem. Rev.

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Main types of crystal structures with different atomic Main types of crystal structures with different atomic defects (point, volume, planar and linear) are considered using defects (point, volume, planar and linear) are considered using inorganic compounds as an example. The review presents the inorganic compounds as an example. The review presents the results of composite analysis of such real structures. Their results of composite analysis of such real structures. Their symmetry, ordering, ways of description, nomenclature and the symmetry, ordering, ways of description, nomenclature and the possibility of the diagnostics from diffraction patterns are dis-possibility of the diagnostics from diffraction patterns are discussed. The results of studies provide evidence that polymorphism cussed. The results of studies provide evidence that polymorphism is typical of real crystal structures. The bibliography includes 101 is typical of real crystal structures. The bibliography includes 101 references references. .

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On rare-earth clustering in flourite type solid solutions MF2REF3

Cited by 14 publications

References 3 publications

Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure

Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure

Crystal structures of inorganic compounds with atomic defects

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On rare-earth clustering in flourite type solid solutions MF2REF3

Cited by 14 publications

References 3 publications

Mechanosynthesis of the Fast Fluoride Ion Conductor Ba1–xLaxF2+x: From the Fluorite to the Tysonite Structure

Mechanosynthesis of the Fast Fluoride Ion Conductor Ba1–xLaxF2+x: From the Fluorite to the Tysonite Structure

Crystal structures of inorganic compounds with atomic defects

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Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure

Mechanosynthesis of the Fast Fluoride Ion Conductor Ba_1–xLa_xF_2+x: From the Fluorite to the Tysonite Structure