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Updated: Jul 1, 2025
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Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles
Published on: October 27, 2018
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Rotational phase transitions in antifluorite-type osmate and iridate compounds
Summary
Structural transitions in antifluorite compounds are driven by octahedron rotations. These displacive phase transitions are well-explained by a tolerance factor related to ionic radii, with minimal anharmonic effects observed.
Area of Science:
- Solid-state chemistry
- Crystallography
- Materials science
Background:
- Antifluorite-type A2MeX6 compounds exhibit complex structural transitions.
- These transitions are linked to rotations of the MeX6 octahedra, leading to diverse symmetries.
Purpose of the Study:
- Investigate temperature-dependent structural behavior of seven antifluorite compounds.
- Analyze the nature of phase transitions and local distortions using advanced diffraction techniques.
Main Methods:
- Single-crystal X-ray diffraction at variable temperatures.
- Refinement of anharmonic atomic displacement parameters.
- Analysis of structural transitions in relation to ionic radii and phonon modes.
Main Results:
- Observed structural transitions driven by MeX6 octahedron rotations.
- Refinements indicated minimal anharmonic effects, suggesting displacive transitions.
- Large harmonic displacement parameters pointed to soft phonon modes across the Brillouin zone.
Conclusions:
- Phase transitions in these antifluorites are predominantly displacive.
- The occurrence of rotational transitions is well-described by a tolerance factor.
- Soft phonon modes play a significant role in the observed structural instabilities.
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