Nanoscale percolation in doped BaZrO3 for high proton mobility

Draber, Fabian M.; Ader, Christiane; Arnold, John P.; Eisele, Sebastian; Grieshammer, Steffen; Yamaguchi, Shu; Martin, Manfred

doi:10.1038/s41563-019-0561-7

Cited by 93 publications

(150 citation statements)

References 49 publications

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“…The preferential proton conduction partially cancels the strong trapping effect of densely populated dopants, resulting in a minor reduction of the proton diffusivity in highly doped BaZrO3. Draber et al also reported the preferential proton conduction along the Y network as nanoscale percolation [19], where the proton diffusivity was estimated in a similar firstprinciples manner to that in Ref. [18].…”

Section: Toyoura Et Al Theoretically Clarified the Detailed Interactmentioning

confidence: 82%

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

Fujii¹,

Toyoura²,

Uda³

et al. 2020

Preprint

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We theoretically revisit the proton diffusivity in yttrium-doped barium zirconate (Y-doped BaZrO<sub>3</sub>) with realistic dopant configurations under processing conditions. In a recent study employing the replica exchange Monte Carlo method, the equilibrium Y configurations at typical sintering temperatures were shown to deviate from the random configuration assumed in earlier theoretical studies. In the present study, we took this observation into account and evaluated the effect of the Y configuration on the proton diffusivity. Using the master equation approach based on local diffusion barriers calculated from first principles, the proton diffusivities under realistic Y configurations were estimated to be higher than those in the random configuration. This is explained by the fact that realistic Y configurations have fewer trap sites with deep potential wells compared to the random configuration due to the isolation trend of Y dopants. In addition, the effects of proton-proton interaction and the abundance of preferential conduction pathways are discussed; it is found that both are relatively minor factors compared to the trap site effect in determining the dependence of the proton diffusivity on the Y configurations.<br>

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Section: Toyoura Et Al Theoretically Clarified the Detailed Interactmentioning

confidence: 82%

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

Fujii¹,

Toyoura²,

Uda³

et al. 2020

Preprint

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“…The migration barriers calculated in ref. [ 28 ] systematically increase with the local Y concentration; they are in the range of 0.22–0.35 eV, when one Y is close to the proton, increase to 0.37–0.55 eV for two close by Y, and reach 0.66 eV for three Y close to the proton. The situation in the highly Y‐doped BaZrO 3 layers is further discussed in Section S7 in the Supporting Information.…”

Section: Discussionmentioning

confidence: 98%

“…In addition to the distinctly higher local doping concentration achievable by the 2D arrangement, it also could give rise to an ideally infinite percolation. The latter issue was emphasized recently, [ 28 ] by giving theoretical evidence that at Y‐contents beyond about 10% percolation of the trapping spheres occurs leading to high proton conductivity (the comparatively low threshold value is due to the trapping zone exceeding the atomic size; cf. Section S4 in the Supporting Information).…”

Section: Discussionmentioning

confidence: 99%

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2D Doping of Proton Conductors: BaZrO₃‐Based Heterostructures

Ngabonziza

Merkle

Wang

et al. 2020

Advanced Energy Materials

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the major tool in this context. Even though homovalent dopants can be beneficial, it is usually heterovalent doping, which is most effective in generating charge carriers. Introducing an effectively negatively charged dopant (such as replacing a cation by a lower-valent one) will-apart from rather exotic cases-increase the concentration of all effectively positively charged point defects (cation interstitials, anion vacancies, and electron holes) and decrease the concentration of all negatively charged point defects (cation vacancies, anion interstitials, and excess electrons) as long as they are in mutual equilibrium. [1] Introducing effectively positively charged defects (e.g., higher-valent cationic substitution) will have the opposite effect. To predict to what degree this occurs, whether, e.g., the dopant concentrations are primarily ionically or electronically compensated, is a matter of defect chemistry. For the sake of precision, the homogeneous introduction of effectively charged foreign elements in the form of point defects will be termed 0D doping in the following. Here, the impurities are usually distributed randomly, and compensating counter charges are locally trapped and/or free beyond the Bjerrum length, at which electrostatic and thermal energies are equal. While the trapped carrier may be potentially mobile around the dopant, i.e., within the trapping zone (see Figure 1a,b), longrange transport requires detrapping. Figure 1 illustrates doping mechanisms of ionic conductors of various dimensionalities. Higher-dimensional doping has recently been explored as alternative doping strategy, potentially overcoming, e.g., limited solubility and charge-carrier trapping issues associated with 0D doping. It has been the availability of sophisticated thin film preparation techniques, that lets higher-dimensional doping come to the fore. If, e.g., in an epitaxial film of a layered compound a complete cationic layer is-in an atomically sharp fashion-replaced by a layer with a heterovalent cation, the whole 2D defect will be charged and the counter charge is generated in the adjacent space-charge zones. One could also think of this 2D doping situation as a 2D arrangement of charged point defects (see Figure 1c). Such an ordering constitutes perfect percolation along the layer, but may also be more easily interrupted by, e.g., impurities or stacking faults. Even more easily interrupted is transport in a 1D doping scenario (1D ordering of point defects). Importantly, in the 0D doping case, the total number (volume integrated) of free charge carriers increases with distance to the dopants, because of the 3D distribution, Ionically conducting oxide heterostructures provide ideal geometries for revealing interfacial effects in solid state ionics. Beyond that, they can provide a high density of heterointerfaces and thus allow for reliable studies of interfacial phenomena with respect to fundamental understanding as well as with respect to nanoionic applications. Substituting an entire single layer rather than random...

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“…Since completion of the core functionality, MOCASSIN has been used successfully for in-house projects investigating fast ion conductors. [18][19][20] With MOCASSIN, we aim to improve accessibility to MC and reduce the need for system-specific developments. We do not aim at providing a truly universal solid-state MC program; instead, MOCASSIN targets the simulation of ionic transport in crystals with moderately complex models based on data from first-principles calculations.…”

Section: Introductionmentioning

confidence: 99%

MOCASSIN: Metropolis and kineticMonte Carlofor solid electrolytes

Eisele

Grieshammer

2020

J Comput Chem

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The combination of density functional theory and Monte Carlo simulations is a powerful approach for the atomistic modeling of defect transport in solid electrolytes. The present contribution introduces the MOCASSIN software (Monte Carlo for Solid State Ionics) for kinetic and Metropolis Monte Carlo simulations of crystalline materials. MOCASSIN combines model building, visualization, and simulation, aiming to provide accessible MC for end users. Developed for the investigation of solid electrolytes, MOCASSIN is ideal for screening common variation parameters, such as temperature and doping fraction. The input effort is minimized using space groups for processing symmetry. The graphical interface for model building allows complex model input, including multiple mobile species, multiple migration paths, small polaron hopping, vehicle movements, multiple complex migration mechanisms, and custom interaction clusters. The software is provided free of charge for noncommercial usage.

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Nanoscale percolation in doped BaZrO3 for high proton mobility

Cited by 93 publications

References 49 publications

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

2D Doping of Proton Conductors: BaZrO₃‐Based Heterostructures

MOCASSIN: Metropolis and kineticMonte Carlofor solid electrolytes

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Nanoscale percolation in doped BaZrO3 for high proton mobility

Cited by 93 publications

References 49 publications

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

Theoretical Study on Proton Diffusivity in Y-Doped BaZrO3 with Realistic Dopant Configurations

2D Doping of Proton Conductors: BaZrO3‐Based Heterostructures

MOCASSIN: Metropolis and kineticMonte Carlofor solid electrolytes

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Product

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2D Doping of Proton Conductors: BaZrO₃‐Based Heterostructures