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Chemical order and local structure of the lead-free relaxor ferroelectric (Na1/2Bi1/2)TiO3

Gröting, Melanie and Hayn, Silke and Albe, Karsten (2011):
Chemical order and local structure of the lead-free relaxor ferroelectric (Na1/2Bi1/2)TiO3.
In: Journal of Solid State Chemistry, Elsevier Science Publishing Company, pp. 2041-2046, 184, (8), [Online-Edition: http://www.sciencedirect.com/science/article/pii/S0022459611...],
[Article]

Abstract

The A-site mixed perovskite sodium bismuth titanate (Na1/2Bi1/2)TiO3 (NBT) is investigated by means of first-principles calculations based on density functional theory. By studying different geometries with varying occupations of the A-site, the influence of chemical order on the thermodynamic stability and local structure is explored. We find that the hybridization of Bi 6sp with O 2p-states leads to stereochemically active Bi3+ lone pairs and increases the stability of structures with high Bi concentrations in {001}-planes. This goes along with displacive disorder on the oxygen sublattice, which up to now has been neglected in experimental studies. The calculated ordering energies are, however, small as compared to the thermal energy and therefore only short-range chemical order can be expected in experiments. Thus, it is conceivable that chemically ordered local areas can act as nucleation sites for polar nano-regions, which would explain the experimentally observed relaxor behavior of NBT.

Item Type: Article
Erschienen: 2011
Creators: Gröting, Melanie and Hayn, Silke and Albe, Karsten
Title: Chemical order and local structure of the lead-free relaxor ferroelectric (Na1/2Bi1/2)TiO3
Language: English
Abstract:

The A-site mixed perovskite sodium bismuth titanate (Na1/2Bi1/2)TiO3 (NBT) is investigated by means of first-principles calculations based on density functional theory. By studying different geometries with varying occupations of the A-site, the influence of chemical order on the thermodynamic stability and local structure is explored. We find that the hybridization of Bi 6sp with O 2p-states leads to stereochemically active Bi3+ lone pairs and increases the stability of structures with high Bi concentrations in {001}-planes. This goes along with displacive disorder on the oxygen sublattice, which up to now has been neglected in experimental studies. The calculated ordering energies are, however, small as compared to the thermal energy and therefore only short-range chemical order can be expected in experiments. Thus, it is conceivable that chemically ordered local areas can act as nucleation sites for polar nano-regions, which would explain the experimentally observed relaxor behavior of NBT.

Journal or Publication Title: Journal of Solid State Chemistry
Volume: 184
Number: 8
Publisher: Elsevier Science Publishing Company
Uncontrolled Keywords: Perovskite, Relaxor, NBT, Chemical order, Local structure
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > C - Modelling > Subproject C1: Quantum mechanical computer simulations for electron and defect structure of oxides
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > C - Modelling
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio)
Date Deposited: 22 Feb 2012 16:26
Official URL: http://www.sciencedirect.com/science/article/pii/S0022459611...
Additional Information:

SFB 595 C1

Identification Number: doi:10.1016/j.jssc.2011.05.044
Funders: This work has been financially supported by the LOEWE-Center “Adaptronics—Research, Innovation, Application” and by the DFG Center of Excellence 595 “Electrical Fatigue in Functional Materials”., Moreover, this work was made possible by grants for computing time on supercomputers at HRZ Darmstadt.
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