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Acta Materialia 58 (2010) 3764-3772


Structure of Cs[NbWO] analysed by focal-series reconstruction and crystallographic image processing

by Juri Barthel, Thomas E. Weirich, Gerhard Cox, Hartmut Hibst, and Andreas Thust

The structure of the oxygen sub-lattice in Cs0.5[Nb2.5W2.5O14] has been investigated for the first time by advanced electron-optical methods. Since the material resembles the crystal structure of the so-called M1 phase of Mo-V-Nb-Te-O, which is the best catalyst for the selective oxidation of propane to acrylic acid, the structure analysis of the oxygen sub-lattice can contribute substantially to a better understanding of this catalytic process.

In the present study, the so far only partially known structure of the complex metal oxide Cs0.5[Nb2.5W2.5O14] has been investigated by combining modern methods of high-resolution transmission electron microscopy with crystallographic image processing techniques.

Average atom positions in the añb plane are determined from the phase of the exit-plane wave function, which was numerically reconstructed from a focal series of spherical-aberration-corrected electron micrographs. The experimentally determined atom positions agree well with a structure model obtained by first-principles calculations for the underlying M5O14 (M = Nb, W) framework. Moreover, several deviations from the periodic structure, which may influence the catalytic properties of the structurally similar M1 phase, have been observed. The obtained results demonstrate that aberration-corrected high-resolution transmission electron microscopy is a reliable alternative for the analysis of periodic structures, in particular when traditional methods for crystallographic structure determination like XRD or neutron diffraction cannot be applied.

Further reading:

Juri Barthel, Thomas E. Weirich, Gerhard Cox, Hartmut Hibst, and Andreas Thust:
Structure of Cs[NbWO] analysed by focal-series reconstruction and crystallographic image processing, Acta Materialia 58 (2010) 3764-3772.

   
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