Revisiting the structures and phase transitions of Ba2NaNb5O15
Journal Article
·
· Journal of Applied Crystallography (Online)
- European Synchrotron Radiation Facility (ESRF), Grenoble (France)
- University of Augsburg (Germany)
- University of British Columbia, Vancouver, BC (Canada)
The room-temperature and low-temperature structure(s) of Ba2NaNb5O15 (BNN) have been debated since the structure was proposed in the 1960s. This work revisits the structures and phase transitions of BNN, combining high-resolution X-ray and neutron powder diffraction with density functional theory calculations. Temperature-dependent high-resolution X-ray powder diffraction patterns are collected from 4 to 918 K, and sequential batch Rietveld refinement using a symmetry mode approach to describe the structure is used to extract the main structural changes as a function of temperature. The data show that the average structure of BNN is best described by the Ama2 space group, and no other structural phase transitions were observed below the ferroelastic transition. The symmetry mode analysis, combining results from diffraction and density functional theory, shows significant octahedral tilting and corrugations of both the A1 and A2 sites along the c direction. A strong correlation between the spontaneous strain and the octahedral tilting was observed, and a potential connection with emerging microstructure at low temperatures is proposed, all enabled by the symmetry mode approach used in this work.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
- Sponsoring Organization:
- Deutsche Forschungsgemeinschaft; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 2471521
- Journal Information:
- Journal of Applied Crystallography (Online), Journal Name: Journal of Applied Crystallography (Online) Journal Issue: 5 Vol. 56; ISSN 1600-5767
- Publisher:
- International Union of CrystallographyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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