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Structural insights into M 2 O–Al 2 O 3 –WO 3 ( M = Na, K) system by electron diffraction tomography
Author(s) -
Andrusenko Iryna,
Krysiak Yaşar,
Mugnaioli Enrico,
Gorelik Tatiana E.,
Nihtianova Diana,
Kolb Ute
Publication year - 2015
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520615007994
Subject(s) - electron diffraction , diffraction , electron backscatter diffraction , materials science , nanocrystalline material , reflection high energy electron diffraction , crystallography , powder diffraction , crystallite , ab initio , scattering , chemistry , nanotechnology , physics , optics , quantum mechanics
The M 2 O–Al 2 O 3 –WO 3 ( M = alkaline metals) system has attracted the attention of the scientific community because some of its members showed potential applications as single crystalline media for tunable solid‐state lasers. These materials behave as promising laser host materials due to their high and continuous transparency in the wide range of the near‐IR region. A systematic investigation of these phases is nonetheless hampered because it is impossible to produce large crystals and only in a few cases a pure synthetic product can be achieved. Despite substantial advances in X‐ray powder diffraction methods, structure investigation on nanoscale is still challenging, especially when the sample is polycrystalline and the structures are affected by pseudo‐symmetry. Electron diffraction has the advantage of collecting data from single nanoscopic crystals, but it is frequently limited by incompleteness and dynamical effects. Automated diffraction tomography (ADT) recently emerged as an alternative approach able to collect more complete three‐dimensional electron diffraction data and at the same time to significantly reduce dynamical scattering. ADT data have been shown to be suitable for ab initio structure solution of phases with large cell parameters, and for detecting pseudo‐symmetry that was undetected in X‐ray powder data. In this work we present the structure investigation of two hitherto undetermined compounds, K 5 Al(W 3 O 11 ) 2 and NaAl(WO 4 ) 2 , by a combination of electron diffraction tomography and precession electron diffraction. We also stress how electron diffraction tomography can be used to obtain direct information about symmetry and pseudo‐symmetry for nanocrystalline phases, even when available only in polyphasic mixtures.