Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

Groszewicz, Pedro B. and Gröting, Melanie and Breitzke, Hergen and Jo, Wook and Albe, Karsten and Buntkowsky, Gerd and Rödel, Jürgen :
Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3.
[Online-Edition: http://doi.org/10.1038/srep31739]
In: Scientific Reports, 6 31739 (1-11). ISSN 2045-2322
[Article] , (2016)
Note:
SFB 595

Official URL: http://doi.org/10.1038/srep31739

Abstract

Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR)spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG)in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties.

Item Type:	Article
Erschienen:	2016
Creators:	Groszewicz, Pedro B. and Gröting, Melanie and Breitzke, Hergen and Jo, Wook and Albe, Karsten and Buntkowsky, Gerd and Rödel, Jürgen
Title:	Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3
Language:	English
Abstract:	Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR)spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG)in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties.
Journal or Publication Title:	Scientific Reports
Volume:	6
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 11 Department of Materials and Earth Sciences > Material Science > Nonmetallic-Inorganic Materials 07 Fachbereich Chemie 07 Fachbereich Chemie > Physical Chemistry Zentrale Einrichtungen Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
Date Deposited:	20 Sep 2016 10:17
Official URL:	http://doi.org/10.1038/srep31739
Additional Information:	SFB 595
Identification Number:	doi:10.1038/srep31739
Funders:	The authors would like to thank Prof. George Rossetti and Prof. Ian Reaney for very fruitful discussions. This work has been financially supported by the Collaborative Research Center SFB 595 “Electrical Fatigue in Functional Materials” of, the Deutsche Forschungsgemeinschaft (DFG). WJ wishes to acknowledge also the financial support by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT and future Planning (No. 2014R1A2A1A11053597). We acknowledge grants for computing time on the “Lichtenberg” high-performance computer at TU Darmstadt.
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