Thermodynamics of mono- and di-vacancies in barium titanate

Erhart, Paul; Albe, Karsten

doi:10.1063/1.2801011

Cited by 135 publications

(120 citation statements)

References 65 publications

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“…4 only emphasizes the most probable vacancy formation location at the interface independent of the existence of other defects in the material. Oxygen vacancies, typically positively charged in similar oxides 39,40 , lead to electrostatic interactions that alter the energetics of vacancies nearby. Furthermore, the formation of equilibrium space-charge regions 7,39,41,42 at the interface can lead to vacancy-rich dislocation cores and vacancy-depleted spacecharge zones, which would further influence the oxygen vacancy energy and defect concentration.…”

Section: Resultsmentioning

confidence: 99%

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

et al. 2014

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Exploiting the promise of nanocomposite oxides necessitates a detailed understanding of the dislocation structure at the interfaces, which governs diverse and technologically relevant properties. Here we report atomistic simulations demonstrating a strong dependence of the dislocation structure on the termination chemistry at the SrTiO 3 /MgO heterointerface. The SrO-and TiO 2 -terminated interfaces exhibit distinct nearest neighbour arrangements between cations and anions, leading to variations in local electrostatic interactions across the interface that ultimately dictate the dislocation structure. Networks of dislocations with different Burgers vectors and dislocation spacing characterize the two interfaces. These networks in turn influence the overall stability of and the behaviour of oxygen vacancies at the heterointerface, which will dictate vital properties such as mass transport at the interface. To date, the observed correlation between the dislocation structure and the termination chemistry at the interface has not been recognized, and offers novel avenues for fine-tuning oxide nanocomposites with enhanced functionalities.

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Section: Resultsmentioning

confidence: 99%

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

et al. 2014

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“…For example, this setup corresponds to dopant-oxygen vacancy complexes in transition metal doped perovskites. It has been reported [15][16][17] that such complexes form immediately during the synthesis process, that they have much slower relaxation times than the free dipoles related to the ferroelectric soft mode, and that different relative orientations towards the spontaneous polarization of the host ferroelectric material are possible. In the present study, we assume fixed defect dipoles, which is a rather realistic approximation at low and ambient temperatures during the time span of a typical ECE measurement, cf.…”

Section: Polar Complexesmentioning

confidence: 99%

“…2,4,6,18,19 In particular, experimental and theoretical investigations reveal the important role of transition metal doping on fatigue behavior in ferroelectric perovskites. 12,[15][16][17] It has been found that an internal bias field builds up in field polarized (poled) Cr doped BTO, which could be related to the alignment of defect dipoles with the overall polarization. 12 In this context Erhart and co-workers performed detailed ab initio based transition state theory simulations on transition metal doped perovskites.…”

Section: Introductionmentioning

confidence: 99%

“…12 In this context Erhart and co-workers performed detailed ab initio based transition state theory simulations on transition metal doped perovskites. [15][16][17] They found that polar O-vacancy dopant complexes, which induce local dipoles, form immediately. It is most favorable if these dipoles align parallel to the overall polarization.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10][11][12][13][14][15][16][17] Both, doping and defects, influence remanent polarization and polarization switching, which are important for the caloric response. Evidently, even the modification of the ferroelectric phase diagram under such doping is still unclear.…”

Section: Introductionmentioning

confidence: 99%

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Influence of defects on ferroelectric and electrocaloric properties ofBaTiO3

Grünebohm

Nishimatsu

2016

Phys. Rev. B

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We report modifications of the ferroelectric and electrocaloric properties of BaTiO3 by defects. For this purpose, we have combined ab initio-based molecular dynamics simulations with a simple model for defects. We find that different kinds of defects modify the ferroelectric transition temperatures and polarization, reduce the thermal hysteresis of the transition and are no obstacle for a large caloric response. For a locally reduced polarization the ferroelectric transition temperature and the adiabatic response are slightly reduced. For polar defects an intriguing picture emerges. The transition temperature is increased by polar defects and the temperature range of the large caloric response is broadened. Even more remarkable, we find an inverse caloric effect in a broad temperature range.

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Using Metadynamics to Obtain the Free Energy Landscape for Cation Diffusion in Functional Ceramics: Dopant Distribution Control in Rare Earth‐Doped BaTiO₃

Ward

Freeman

Dean

et al. 2019

Adv Funct Materials

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Barium titanate is the dielectric material of choice in most multilayer ceramic capacitors (MLCCs) and thus in the production of ≈3 trillion devices every year, with an estimated global market of ≈$8330 million per year. Rare earth dopants are regularly used to reduce leakage currents and improve the MLCC lifetime. Simulations are used to investigate the ability of yttrium, dysprosium, and gadolinium to reduce leakage currents by trapping mobile oxygen defects. All the rare earths investigated trap oxygen vacancies, however, dopant pairs are more effective traps than isolated dopants. The number of trapping sites increases with the ion size of the dopant, suggesting that gadolinium should be more effective than dysprosium, which contradicts experimental data. Additional simulations on diffusion of rare earths through the lattice during sintering show that dysprosium diffuses significantly faster than the other rare earths considered. As a consequence, its greater ability to reduce oxygen migration is a combination of thermodynamics (a strong ability to trap oxygen vacancies) and kinetics (sufficient distribution of the rare earth in the lattice to intercept the migrating defects).the high activation barriers make events too infrequent for reliable statistics in molecular dynamics. Methods exist which compel the simulation to investigate the high-energy configurations involved in such processes. Metadynamics [1] is a powerful example of this approach that has enabled studies of crystallization, [2] phase transformations, [3] protein interactions, [4] and molecular docking processes [5,6] and recently diffusion processes, [7] providing new insight at the atomic level into complex physics and chemistry. We use it here to investigate how rare earth (RE) dopants in barium titanate (BaTiO 3 ) trap mobile oxygen defects to prevent capacitor breakdown and improve the lifetime of multilayer ceramic capacitors (MLCCs).BaTiO 3 is a ferroelectric perovskite used in many electronic devices. It has a high relative permittivity at room temperature so that high capacitances can be achieved with thin layers in capacitor applications. [8] It is the dielectric used in MLCCs and thus in the production of ≈3 trillion devices every year with an estimated global market of ≈$8.4 B in 2016. [9] The failure of these capacitors [10] is usually ascribed to the diffusion of oxygen ions, which produces a leakage current. As a consequence, BaTiO 3 is frequently doped with RE 3+ ions to trap the mobile oxygen defects and so improve its electrical properties for MLCC applications. [11] The incorporation of these ions affects the microstructure of the ceramic, producing core-shell grain structures that improve the temperature dependence of capacitance for MLCCs [12] as well as their electrical stability. Doping with mid-size (0.9-0.94 Å [13] ) RE 3+ ions (particularly Dy 3+ ) [11,[14][15][16] leads to improved lifetimes for MLCCs.Undoped bulk ceramic BaTiO 3 contains a low concentration of intrinsic oxygen vacancies from the Schottky mechanism [1...

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Thermodynamics of mono- and di-vacancies in barium titanate

Cited by 135 publications

References 65 publications

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

Influence of defects on ferroelectric and electrocaloric properties ofBaTiO3

Using Metadynamics to Obtain the Free Energy Landscape for Cation Diffusion in Functional Ceramics: Dopant Distribution Control in Rare Earth‐Doped BaTiO₃

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Thermodynamics of mono- and di-vacancies in barium titanate

Cited by 135 publications

References 65 publications

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

Influence of defects on ferroelectric and electrocaloric properties ofBaTiO3

Using Metadynamics to Obtain the Free Energy Landscape for Cation Diffusion in Functional Ceramics: Dopant Distribution Control in Rare Earth‐Doped BaTiO3

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Product

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Using Metadynamics to Obtain the Free Energy Landscape for Cation Diffusion in Functional Ceramics: Dopant Distribution Control in Rare Earth‐Doped BaTiO₃