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- Title
Defect Structures of La<sub>1 - y</sub>Sr<sub>y</sub>F<sub>3 - y</sub>, La<sub>1 - y</sub>BayF<sub>3 - y</sub>, and Nd<sub>1 - y</sub>Ca<sub>y</sub>F<sub>3 - y</sub> (y = 0.05, 0.10) Nonstoichiometric Tysonite Phases.
- Authors
Chernaya, T. S.; Verin, I. A.; Khrykina, O. N.; Bolotina, N. B.
- Abstract
Characteristic features of defect structures of La1 - ySryF3 - y, La1 - yBayF3 - y, and Nd1 - yCayF3 - y (y = 0.05, 0.10) nonstoichiometric phases of different compositions are determined from X-ray diffraction data. Interest in subtle details of their structure is determined by the possibility of ion transport over fluorine vacancies and by a strong compositional dependence of the ionic conductivity. The La0.95Sr0.05F2.95, La0.95Ba0.05F2.95, and Nd0.95Ca0.05F2.95 phases, as well as the La0.9Ba0.1F2.9 phase, crystallize as β-LaF3 (sp. gr. P3c1, Z = 6). The La0.9Sr0.1F2.9 and Nd0.9Ca0.1F2.9 phases lose their superstructure and are described by a cell whose volume is three times smaller (sp. gr. P63/mmc, Z = 2). Defects of crystal structure R1 - yMyF3 - y are not exhausted by vacancies in fluorine positions. All crystals with a "large" cell are twinned according to the merohedral twin law. The majority of atomic positions in models with a "small" cell are split by group symmetry elements and are occupied statistically.
- Subjects
X-ray diffraction; IONIC conductivity; TYSONITE; FLUORINE; CRYSTAL structure
- Publication
Crystallography Reports, 2018, Vol 63, Issue 1, p45
- ISSN
1063-7745
- Publication type
Article
- DOI
10.1134/S1063774518010042