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Solving modulated structures by X-ray and electron crystallography
M T Caldes1, P Deniard, X D Zou
1Institut des Matériaux Jean Rouxel, UMR 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 03, France.
Micron (Oxford, England : 1993)
|February 13, 2001
Summary
Combining X-ray and electron crystallography reveals weak modulations in complex structures. Electron diffraction clearly shows modulations missed by X-ray diffraction, enabling detailed atomic structure analysis.
Area of Science:
- Crystallography
- Materials Science
- Solid State Chemistry
Background:
- X-ray diffraction (XRD) is standard for structure determination.
- Weakly modulated structures present challenges for XRD due to faint satellite reflections.
- Electron diffraction offers superior sensitivity for detecting weak modulations.
Purpose of the Study:
- To demonstrate the combined power of X-ray and electron crystallography for studying modulated structures in powders.
- To analyze the complex modulated compound Sr(1.4)Ta(0.6)O(2.9).
- To overcome limitations of XRD for weak modulations.
Main Methods:
- Powder X-ray diffraction (XRD).
- Selected Area Electron Diffraction (SAED).
- High-Resolution Electron Microscopy (HREM).
- Advanced image processing techniques for electron microscopy data.
Main Results:
- XRD provided average structures for Sr(1.4)Ta(0.6)O(2.9).
- Electron diffraction clearly identified weak modulations.
- HREM images, enhanced by image processing, revealed detailed modulation information.
- Atomic structure interpretation was facilitated by enhanced HREM data.
Conclusions:
- Combining XRD and electron crystallography is powerful for studying modulated structures, especially those with weak modulations.
- Electron diffraction is crucial for detecting modulations missed by XRD.
- Image processing techniques enhance HREM data for precise atomic structure determination.