Studies of effects of trivalent impurity ions on the transition to the superionic state of fluorites

Catlow, C. Richard A.; Comins, J. D.; Germano, F. A.; Harley, R. T.; Hayes, W.; Owen, I B

doi:10.1088/0022-3719/14/4/008

Cited by 49 publications

(15 citation statements)

References 14 publications

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“…The addition of trivalent cations such as Y 3+ has been shown to increase the low temperature ionic conductivity of halide fluorite compounds [483] and to substantially depress the temperature at which the type-II superionic transition occurs [484,485]. In the (Ca 1−x Y x )F 2+x system, T c falls from 1430 K at x = 0 to ≈1200 K for x = 0.09 [484]. Single crystal neutron diffraction studies of an x = 0.06 sample showed a gradual increase in the occupancy of the F2 sites with increasing temperature and, at T > ≈1100 K, the ratio of the occupancies of the F1 and F2 positions approaches the value 1 : 2.…”

Section: Anion-excess Fluorite: (Camentioning

confidence: 99%

Superionics: crystal structures and conduction processes

2004

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Superionic conductors are compounds that exhibit exceptionally high values of ionic conductivity within the solid state. Indeed, their conductivities often reach values of the order of 1 −1 cm −1 , which are comparable to those observed in the molten state. Following Faraday's first observation of high ionic conductivity within the solids β-PbF 2 and Ag 2 S in 1836, a fundamental understanding of the nature of the superionic state has provided one of the major challenges in the field of condensed matter science. However, experimental and theoretical approaches to their study are often made difficult by the extensive dynamic structural disorder which characterizes superionic conduction and the inapplicability of many of the commonly used approximations in solid state physics. Nevertheless, a clearer picture of the nature of the superionic state at the ionic level has emerged within the past few decades. Many different techniques have contributed to these advances, but the most significant insights have been provided by neutron scattering experiments and molecular dynamics simulations. This review will summarize the state of current knowledge concerning the crystal structures and conduction processes of superionic conductors, beginning with a comparison of the behaviour of two of the most widely studied binary compounds, AgI and β-PbF 2 . Each can be considered a parent of two larger families of highly conducting compounds which are related by either chemical or structural means. These include perovskite-structured oxides and Li + containing spinel-structured compounds, which have important commercial applications in fuel cells and lightweight batteries, respectively. In parallel with these discussions, the relative importance of factors such as bonding character and the properties of the mobile and immobile ions (charge, size, polarizability, etc) in promoting the extensive lattice disorder which characterizes superionic behaviour will be assessed and the possibilities for predicting a priori which compounds will display high ionic conductivity discussed.

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Section: Anion-excess Fluorite: (Camentioning

confidence: 99%

Superionics: crystal structures and conduction processes

2004

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“…Вопрос о влиянии легирования кристаллов на фарадеевский переход рассматривался на основе анализа данных, полученных методами термического анализа и рассеяния света для твердых растворов Ca 1−x Y x F 2+x [29], Ba 1−x La x F 2+x [6,30], [32]. В этих работах обнаружено, что с ростом концентрации примесного компонента происходит, как правило, расширение температурного интервала существования суперионного состояния флюоритовых кристаллов.…”

Section: температурный интервал фарадеевского перехода равенunclassified

“…Снижение температуры фарадеевского перехода подтверждается экспериментальными результатами измерений коэффициентов упругой податливости кристаллов Ca 0.91 Y 0.09 F 2.09 [29] и Ba 0.607 La 0.393 F 2.393 [11], измерений теплоемкости кристаллов Pb 1−x R x F 2+2x (R = La, Yb; 0 < x < 0.17) [31] и M 1−x U x F 2+2x (M = Ba, Pb; 0 < x < 0.10) [46], а также теоретическими расчетами [15]. Фарадеевский переход происходит при существенно более низких температурах в твердых растворах, чем во флюоритовых матрицах.…”

Section: выращивание монокристаллов и измерения ионной проводимости т...unclassified

Влияние изо- и гетеровалентных замещений катионов на суперионный фарадеевский переход во флюоритовой модификации β-PbF-=SUB=-2-=/SUB=-

Сорокин¹

2022

Физика Твердого Тела

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The influence of isovalent substitutions of Pb2+ by Cd2+ and heterovalent substitutions of Pb2+ by Sc3+ on a superionic Faraday transition in Pb1 – xCdxF2 (x = 0.33) and Pb1 – x ScxF2+x (x = 0.1) solid solutions based on the fluorite-type modification β-PbF2 with sp. gr. Fm¯3m has been studied. The Faraday phase transition can be characterized by the temperature Tλ corresponding to maximum on the heat capacity curve and temperature Tα corresponding to the beginning of the structural disorder anion sublattice. Both of these temperatures are found on the temperature conductivity dependence σdc(T ) of β-PbF2, Pb0.67Cd0.33F2 and Pb0.9Sc0.1F2.1 crystals. The values of Tλ and Tα in solid solutions compared with β-PbF2 matrix (Tλ = 715 ± 10K, Tα = 597 ± 12 K) decrease by 100–110 and 30–45 K for Pb0.67Cd0.33F2 and Pb0.9Sc0.1F2.1, respectively. Decreasing of temperature Tλ leads to an increase in temperature interval of existence of the superionic state. For T > Tλ the anionic conductivity of fluorite-type Pb0.67Cd0.33F2, Pb0.9Sc0.1F2.1, and β-PbF2 crystals reaches anomalously high values of σdc = 1–2 S/cm (873 K) at an ion transfer activation enthalpy equals to Hσ = 0.3 eV.

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“…Rare-earths in alkaline-earth fluorides are known to enhance the superionic conductivity of the host fluorides. 27 This enhancement appears to be linked to a tendency of rare earths to form aggregates of different sizes with intrinsic defects in the fluoride lattice. In alkaline-earth fluorides, defect aggregation has been thoroughly studied by Catlow and his co-workers, 15,[28][29][30][31] with an aim to provide a microscopic description of the aggregation process.…”

Section: Rare-earth Doped Pbfmentioning

confidence: 99%

Theoretical study of native and rare-earth defect complexes in β-PbF2

et al. 2000

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Native and rare-earth-doped point-defects in ␤-PbF 2 are studied in the framework of the pair-potential approximation coupled with the shell model description of the lattice ions. For the perfect lattice, a new set of potential parameters are obtained which reproduce structure, elastic and dielectric constants of PbF 2 very well. The calculated formation energies for native defects suggest that the anion Frenkel disorder is preferred over the cation Frenkel and Schottky-like disorder in PbF 2. The computed temperature behavior of the ionic conductivity agrees very well with the available experimental data. In the rare-earth doped PbF 2 , a site preference of the charge-compensating fluorine interstitial appears to change from nearest to next-nearest neighbor with the increase in the rare-earth ionic radius.

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Studies of effects of trivalent impurity ions on the transition to the superionic state of fluorites

Cited by 49 publications

References 14 publications

Superionics: crystal structures and conduction processes

Superionics: crystal structures and conduction processes

Влияние изо- и гетеровалентных замещений катионов на суперионный фарадеевский переход во флюоритовой модификации β-PbF-=SUB=-2-=/SUB=-

Theoretical study of native and rare-earth defect complexes in β-PbF2

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Studies of effects of trivalent impurity ions on the transition to the superionic state of fluorites

Cited by 49 publications

References 14 publications

Superionics: crystal structures and conduction processes

Superionics: crystal structures and conduction processes

Влияние изо- и гетеровалентных замещений катионов на суперионный фарадеевский переход во флюоритовой модификации &beta;-PbF-=SUB=-2-=/SUB=-

Theoretical study of native and rare-earth defect complexes in β-PbF2

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Влияние изо- и гетеровалентных замещений катионов на суперионный фарадеевский переход во флюоритовой модификации β-PbF-=SUB=-2-=/SUB=-