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Randomly arranged cation-ordered nanoregions in lead-free relaxor ferroelectric K1/2Bi1/2TiO3: Prediction from first-principles study
- Source :
- Journal of Applied Physics. 123:244106
- Publication Year :
- 2018
- Publisher :
- AIP Publishing, 2018.
-
Abstract
- First-principles density functional calculations are performed to investigate the lattice dynamics, Infrared reflectivity, and Raman intensity spectra of a lead-free ferroelectric K1/2Bi1/2TiO3 system. In particular, the A-site cation ordering in K1/2Bi1/2TiO3 and its effects on lattice dynamics and the Raman spectrum are explored. The results suggest that the cation ordering at the A-site in K1/2Bi1/2TiO3 significantly influences its Raman spectra. From the analysis of theoretical and experimental Raman spectra, it is suggested that randomly arranged cation ordered nanoregions with different A-site orderings are formed in K1/2Bi1/2TiO3 samples. The random arrangement is favored by entropy contributions to free energy and may explain the lack of observed long-range A-site cation ordering in K1/2Bi1/2TiO3. Further, it is suggested that partial A-site cation ordering may also occur in K1/2Bi1/2TiO3 favored by kinetic factors during sample preparation. The Born effective charges of K and Bi ions at the A-site are computed and found to be significantly disparate, thereby suggesting hetero-polar activity at the A-site in K1/2Bi1/2TiO3. The formation of A-site hetero-polar cation ordered nanoregions and their random or/and partially ordered arrangement in K1/2Bi1/2TiO3 may play an important role in the determination of its relaxor properties apart from the dominant role played by polar nanoregions. The computed Infrared reflectivity and Raman intensity spectra are expected to provide benchmark first-principles results for further analysis of experimental spectra and results.
- Subjects :
- 010302 applied physics
Materials science
Condensed matter physics
General Physics and Astronomy
02 engineering and technology
021001 nanoscience & nanotechnology
Kinetic energy
01 natural sciences
Ferroelectricity
Spectral line
Ion
symbols.namesake
Ab initio quantum chemistry methods
0103 physical sciences
symbols
Polar
Density functional theory
0210 nano-technology
Raman spectroscopy
Subjects
Details
- ISSN :
- 10897550 and 00218979
- Volume :
- 123
- Database :
- OpenAIRE
- Journal :
- Journal of Applied Physics
- Accession number :
- edsair.doi...........e5b8e70123312118999f4e690c20badd