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Phase transitions in the relaxor-like sodium bismuth titanate studied by density functional theory calculations

Wednesday (28.09.2016)
10:30 - 10:45
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Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) is a ferroelectric relaxor-like material at room temperature and has interesting electrical and piezoelectric properties. [1]

Below and around room temperature the space group of NBT is close to the rhombohedral R3c with slight deviations to a monoclinic symmetry. However, the space groups and phase transitions at temperatures higher than 500 K are not fully understood, especially the existence of the orthorhombic phase which has only been seen in electron diffraction, but not in XRD.

In this work we investigate the phase transition on an atomistic level by density functional theory calculations. Specifically, we take into account octahedral tilts, chemical order of the A-cations and displacements of A-cations. We study the system by looking at energy barriers between different phases from nudged elastic band calculations and ab-initio molecular dynamics. Further, we try to explain the origin of polar nanoregions. [2]

[1] Reichmann, K et al., Materials 8, 8467 - 8495 (2015)

[2] K.-C. Meyer, \textit{et\,al.}, J. Solid State Chem. 227, 117 - 122 (2015)

Kai-Christian Meyer
Darmstadt University of Technology
Additional Authors:
  • Leonie Koch
    Darmstadt University of Technology
  • Prof. Dr. Karsten Albe
    Darmstadt University of Technology