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The incommensurate modulation of the structure of Sr2Nb2O7
Peter Daniels1, Rafael Tamazyan, Christine A Kuntscher
1Laboratory for Crystallography, Universität Bayreuth, Germany. peter.daniels@uni-bayreuth.de
Acta Crystallographica. Section B, Structural Science
|November 29, 2002
Summary
The incommensurately modulated structure of strontium niobate (Sr(2)Nb(2)O(7)) at room temperature was revealed by X-ray diffraction. Internal strain around strontium atoms drives this modulation, affecting NbO(6) octahedra and Sr atom positions.
Area of Science:
- Solid State Chemistry
- Crystallography
- Materials Science
Background:
- Strontium niobate (Sr(2)Nb(2)O(7)) exhibits complex crystal structures.
- Understanding its modulated structure is key to its properties.
Purpose of the Study:
- To determine the incommensurately modulated structure of Sr(2)Nb(2)O(7) at room temperature.
- To identify the driving forces behind the observed structural modulation.
Main Methods:
- Single-crystal X-ray diffraction was performed at room temperature.
- Synchrotron radiation and a CCD area detector were utilized for data collection.
- Superspace group analysis was employed to refine the modulated structure.
Main Results:
- Sr(2)Nb(2)O(7) was found to crystallize in superspace group Cmc2(1)(alpha00)0s0.
- Internal strain around Sr atoms at slab interfaces was identified as the modulation driver.
- Modulation involves rotations of NbO(6) octahedra and Sr atom displacements.
Conclusions:
- The study elucidates the complex modulated structure of Sr(2)Nb(2)O(7).
- The findings provide insights into structure-property relationships in layered perovskite materials.