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Positive and negative electrocaloric effect in BaTiO3 in the presence of defect dipoles

Ma, Yang-Bin and Grünebohm, Anna and Meyer, Kai-Christian and Albe, Karsten and Xu, Bai-Xiang (2016):
Positive and negative electrocaloric effect in BaTiO3 in the presence of defect dipoles.
In: Physical Review B, pp. 094113, 94, (9), ISSN 2469-9950, [Online-Edition: http://dx.doi.org/10.1103/PhysRevB.94.094113],
[Article]

Abstract

The influence of defect dipoles on the electrocaloric effect (ECE) in acceptor doped BaTiO3 is studied by means of lattice-based Monte-Carlo simulations using a Ginzburg-Landau type effective Hamiltonian. Oxygen vacancy-acceptor associates are described by fixed local dipoles with orientation parallel or antiparallel to the external field. By a combination of canonical and microcanonical simulations the ECE is directly evaluated. Our results reveal that in the case of antiparallel defect dipoles the ECE can be positive or negative depending on the dipole density. Moreover, a transition from a negative to positive ECE can be observed when the external field increases. These transitions are due to the delicate interplay of internal and external fields and are explained by the domain structure evolution and related field-induced entropy changes. The results are in good qualitative agreement to those obtained by molecular dynamics simulations employing an ab initio based effective Hamiltonian. Finally, a modified electrocaloric cycle, which makes use of the negative ECE in the presence of defect dipoles, is proposed to enhance the cooling effect.

Item Type: Article
Erschienen: 2016
Creators: Ma, Yang-Bin and Grünebohm, Anna and Meyer, Kai-Christian and Albe, Karsten and Xu, Bai-Xiang
Title: Positive and negative electrocaloric effect in BaTiO3 in the presence of defect dipoles
Language: English
Abstract:

The influence of defect dipoles on the electrocaloric effect (ECE) in acceptor doped BaTiO3 is studied by means of lattice-based Monte-Carlo simulations using a Ginzburg-Landau type effective Hamiltonian. Oxygen vacancy-acceptor associates are described by fixed local dipoles with orientation parallel or antiparallel to the external field. By a combination of canonical and microcanonical simulations the ECE is directly evaluated. Our results reveal that in the case of antiparallel defect dipoles the ECE can be positive or negative depending on the dipole density. Moreover, a transition from a negative to positive ECE can be observed when the external field increases. These transitions are due to the delicate interplay of internal and external fields and are explained by the domain structure evolution and related field-induced entropy changes. The results are in good qualitative agreement to those obtained by molecular dynamics simulations employing an ab initio based effective Hamiltonian. Finally, a modified electrocaloric cycle, which makes use of the negative ECE in the presence of defect dipoles, is proposed to enhance the cooling effect.

Journal or Publication Title: Physical Review B
Volume: 94
Number: 9
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Mechanics of functional Materials
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
11 Department of Materials and Earth Sciences > Material Science
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ)
11 Department of Materials and Earth Sciences
Zentrale Einrichtungen
Date Deposited: 30 Sep 2016 10:54
Official URL: http://dx.doi.org/10.1103/PhysRevB.94.094113
Identification Number: doi:10.1103/PhysRevB.94.094113
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