Modulated structure of potassium sodium strontium barium niobates (KNSBN): harmonic solution
| Autor: | Dominik Schaniel, Audrey Surmin, Pierre Fertey, Theo Woike |
|---|---|
| Přispěvatelé: | Laboratoire de Cristallographie et modélisation des matériaux minéraux et biologiques (LCM3B), Université Henri Poincaré - Nancy 1 (UHP)-Centre National de la Recherche Scientifique (CNRS) |
| Rok vydání: | 2006 |
| Předmět: |
Strontium
Doping Inorganic chemistry chemistry.chemical_element Barium 02 engineering and technology General Medicine Crystal structure 010402 general chemistry 021001 nanoscience & nanotechnology Superspace 01 natural sciences Ferroelectricity General Biochemistry Genetics and Molecular Biology 0104 chemical sciences Tetragonal crystal system Crystallography chemistry Modulation [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] 0210 nano-technology ComputingMilieux_MISCELLANEOUS |
| Zdroj: | HAL Acta Crystallographica Section B: Structural Science Acta Crystallographica Section B: Structural Science, International Union of Crystallography, 2006, pp.228-235 |
| ISSN: | 0108-7681 |
| DOI: | 10.1107/s0108768106001510 |
| Popis: | The structures of two specimens of the (K1 − y Na y )2F − 2(Sr x Ba1 − x )2 − F Nb2O6 family (KNSBN) have been solved and refined (x I = 0.6, y I = 0.45, F I = 1.07 and x II = 0.72, y II = 0.45, F II = 1.08). The KNSBN compounds appear to be incommensurately modulated, as described in a five-dimensional superspace approach with the tetragonal P4bm (pp1/2, p − p1/2) superspace group. Their modulation wavevectors are almost independent of the composition. The description of the modulation is restricted to first-order harmonics in order to limit the number of refined parameters. The modulation mainly affects the positions of the O atoms and their displacements depend on the Sr/Ba ratio. The structural models for the two compounds are not only almost identical, but also analoguous to the structural model of the Sr x Ba1 − x Nb2O6 parent compound: doping with K+ and Na+ cations has no significant influence on the incommensurate modulation, contrary to the strong dependence observed for the physical properties. |
| Databáze: | OpenAIRE |
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