Defect Structures of La1 – ySr y F3 – y, La1 – yBa y F3 – y, and Nd1 – yCa y F3 – y (y = 0.05, 0.10) Nonstoichiometric Tysonite Phases
| Autor: | T. S. Chernaya, Nadezhda B. Bolotina, I. A. Verin, O. N. Khrykina |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Superstructure Materials science chemistry.chemical_element General Chemistry Crystal structure 010403 inorganic & nuclear chemistry Condensed Matter Physics Group symmetry 01 natural sciences 0104 chemical sciences Crystallography chemistry Phase (matter) 0103 physical sciences Fluorine Ionic conductivity General Materials Science |
| Zdroj: | Crystallography Reports. 63:45-51 |
| ISSN: | 1562-689X 1063-7745 |
| Popis: | Characteristic features of defect structures of La1 – ySr y F3 – y, La1 – yBa y F3 – y, and Nd1 – yCa y F3 – 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 – yM y F3 – 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. |
| Databáze: | OpenAIRE |
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