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Defect structure and ionic conductivity of as-grown R 1–y Sr y F 3–y ( R = Ce, Pr, or Nd) crystals with high SrF 2 content

Defect structure and ionic conductivity of as-grown R 1–y Sr y F 3–y ( R = Ce, Pr, or Nd)... Abstract The structure of defect nonstoichiometric phases of Ce0.88Sr0.12F2.88, Pr0.85Sr0.15F2.85, and Nd0.85Sr0.15F2.85 single crystals has been investigated by X-ray diffraction at room temperature. Crystals R 1–ySryF3–y (R = Ce, Pr, or Nd) belong to the tysonite structural type (LaF3), which has two forms (α and β). The morphotropic transition from the trigonal β form of the crystals to the hexagonal α form is confirmed, which was previously found for the first time when analyzing the nonstoichiometric phase of La1–ySryF3–y with a SrF2 content above 10 mol % (y ≥ 0.1). Temperature dependences of fluorine-ion conductivity are obtained. It is established that the conductivity of the α form of Ce0.88Sr0.12F2.88 and R0.85Sr0.15F2.85 crystals (R = Pr or Nd) is lower than that for the β form of R0.95Sr0.05F2.95 (R = La–Nd) by 1–2 orders of magnitude. The sublattice of fluorine atoms in the α-form crystals is characterized by an elevated (in comparison with the β form) content of vacancies and more uniform structural and dynamic properties, which leads to a decrease in the mean diffusion mobility of fluorine ions and an increase in the ion-transport activation enthalpy. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Crystallography Reports Springer Journals

Defect structure and ionic conductivity of as-grown R 1–y Sr y F 3–y ( R = Ce, Pr, or Nd) crystals with high SrF 2 content

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References (18)

Publisher
Springer Journals
Copyright
2017 Pleiades Publishing, Inc.
ISSN
1063-7745
eISSN
1562-689X
DOI
10.1134/s1063774517040083
Publisher site
See Article on Publisher Site

Abstract

Abstract The structure of defect nonstoichiometric phases of Ce0.88Sr0.12F2.88, Pr0.85Sr0.15F2.85, and Nd0.85Sr0.15F2.85 single crystals has been investigated by X-ray diffraction at room temperature. Crystals R 1–ySryF3–y (R = Ce, Pr, or Nd) belong to the tysonite structural type (LaF3), which has two forms (α and β). The morphotropic transition from the trigonal β form of the crystals to the hexagonal α form is confirmed, which was previously found for the first time when analyzing the nonstoichiometric phase of La1–ySryF3–y with a SrF2 content above 10 mol % (y ≥ 0.1). Temperature dependences of fluorine-ion conductivity are obtained. It is established that the conductivity of the α form of Ce0.88Sr0.12F2.88 and R0.85Sr0.15F2.85 crystals (R = Pr or Nd) is lower than that for the β form of R0.95Sr0.05F2.95 (R = La–Nd) by 1–2 orders of magnitude. The sublattice of fluorine atoms in the α-form crystals is characterized by an elevated (in comparison with the β form) content of vacancies and more uniform structural and dynamic properties, which leads to a decrease in the mean diffusion mobility of fluorine ions and an increase in the ion-transport activation enthalpy.

Journal

Crystallography Reports – Springer Journals

Published: Jul 1, 2017

Keywords: Crystallography and Scattering Methods

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