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Pressure-induced phase transitions and structure of chemically ordered nanoregions in the lead-free relaxor ferroelectric Na_{1/2}Bi_{1/2}TiO_{3}

Gröting, Melanie and Kornev, Igor and Dkhil, Brahim and Albe, Karsten (2012):
Pressure-induced phase transitions and structure of chemically ordered nanoregions in the lead-free relaxor ferroelectric Na_{1/2}Bi_{1/2}TiO_{3}.
In: Physical Review B, American Physical Society, pp. 134118(1-10), 86, (13), ISSN 1098-0121,
[Online-Edition: http://dx.doi.org/10.1103/PhysRevB.86.134118],
[Article]

Abstract

We investigate the phase stability of Na1/2Bi1/2TiO3, a prototype lead-free relaxor material, under pressure. By means of total energy calculations within density functional theory, we study the pressure stability of several structures with polar and antipolar distortions, in-phase and out-of-phase tilts, and different chemically ordered configurations. Under positive (compressive) pressure an orthorhombic Pbnm-like phase is stabilized above 3 GPa. At negative (tensile) pressure a non-tilted polar P4mm-like phase is stable. At zero pressure two phases are coexisting. The local chemical configuration determines whether the high-pressure Pbnm-like or another tilted and polar R3c-like structure is favored. Thus, two different variants of pressure phase diagrams depending on the cation arrangement are obtained, which raises the question of the existence of a mixed phase ground state in the disordered system. We discuss the stability of the mixed phase state in terms of lattice and tilt misfits and possible shapes and ferroic properties of the coexisting regions with different average structures. Our results clearly support the view that there are chemically ordered nanoregions with their own local ferroic properties embedded in a chemically disordered ferroelectric matrix representing the ground state.

Item Type: Article
Erschienen: 2012
Creators: Gröting, Melanie and Kornev, Igor and Dkhil, Brahim and Albe, Karsten
Title: Pressure-induced phase transitions and structure of chemically ordered nanoregions in the lead-free relaxor ferroelectric Na_{1/2}Bi_{1/2}TiO_{3}
Language: English
Abstract:

We investigate the phase stability of Na1/2Bi1/2TiO3, a prototype lead-free relaxor material, under pressure. By means of total energy calculations within density functional theory, we study the pressure stability of several structures with polar and antipolar distortions, in-phase and out-of-phase tilts, and different chemically ordered configurations. Under positive (compressive) pressure an orthorhombic Pbnm-like phase is stabilized above 3 GPa. At negative (tensile) pressure a non-tilted polar P4mm-like phase is stable. At zero pressure two phases are coexisting. The local chemical configuration determines whether the high-pressure Pbnm-like or another tilted and polar R3c-like structure is favored. Thus, two different variants of pressure phase diagrams depending on the cation arrangement are obtained, which raises the question of the existence of a mixed phase ground state in the disordered system. We discuss the stability of the mixed phase state in terms of lattice and tilt misfits and possible shapes and ferroic properties of the coexisting regions with different average structures. Our results clearly support the view that there are chemically ordered nanoregions with their own local ferroic properties embedded in a chemically disordered ferroelectric matrix representing the ground state.

Journal or Publication Title: Physical Review B
Volume: 86
Number: 13
Publisher: American Physical Society
Divisions: 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
11 Department of Materials and Earth Sciences > Material Science
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
11 Department of Materials and Earth Sciences
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio)
Date Deposited: 30 Oct 2012 13:07
Official URL: http://dx.doi.org/10.1103/PhysRevB.86.134118
Additional Information:

SFB 595 C1

Identification Number: doi:10.1103/PhysRevB.86.134118
Funders: This work has been financially supported by the LOEWECenter “Adaptronics - Research, Innovation, Application” and by the DFG Collaborative Research Center SFB 595 “Electrical Fatigue in Functional Materials.”, Moreover, this work was made possible by grants for computing time on supercomputers at HRZ Darmstadt., DAAD is acknowledged for supporting the stay of one of us (M.G.) at École Centrale Paris.
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