First Principles Study of Oxygen Incorporation Reactions in Oxides

Holme, Timothy P.; Prinz, Fritz B.

doi:10.14723/tmrsj.35.59

Cited by 2 publications

(2 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is known that under oxygen poor conditions ceria can be reduced leading to the formation of polarons, 48,49 and a number of theoretical studies have been dedicated to this subject. [50][51][52][53][54][55][56] However, we restrict our simulations to conditions where the electronic conductivity is significantly smaller than the ionic conductivity and thus can be neglected.…”

Section: Introductionmentioning

confidence: 99%

Understanding the ionic conductivity maximum in doped ceria: trapping and blocking

Koettgen

Grieshammer

Hein

et al. 2018

Phys. Chem. Chem. Phys.

139

178

View full text Add to dashboard Cite

Materials with high oxygen ion conductivity and low electronic conductivity are required for electrolytes in solid oxide fuel cells (SOFC) and high-temperature electrolysis (SOEC). A potential candidate for the electrolytes, which separate oxidation and reduction processes, is rare-earth doped ceria. The prediction of the ionic conductivity of the electrolytes and a better understanding of the underlying atomistic mechanisms provide an important contribution to the future of sustainable and efficient energy conversion and storage. The central aim of this paper is the detailed investigation of the relationship between defect interactions at the microscopic level and the macroscopic oxygen ion conductivity in the bulk of doped ceria. By combining ab initio density functional theory (DFT) with Kinetic Monte Carlo (KMC) simulations, the oxygen ion conductivity is predicted as a function of the doping concentration. Migration barriers are analyzed for energy contributions, which are caused by the interactions of dopants and vacancies with the migrating oxygen vacancy. We clearly distinguish between energy contributions that are either uniform for forward and backward jumps or favor one migration direction over the reverse direction. If the presence of a dopant changes the migration energy identically for forward and backward jumps, the resulting energy contribution is referred to as blocking. If the change in migration energy due to doping is different for forward and backward jumps of a specific ionic configuration, the resulting energy contributions are referred to as trapping. The influence of both effects on the ionic conductivity is analyzed: blocking determines the dopant fraction where the ionic conductivity exhibits the maximum. Trapping limits the maximum ionic conductivity value. In this way, a deeper understanding of the underlying mechanisms determining the influence of dopants on the ionic conductivity is obtained and the ionic conductivity is predicted more accurately. The detailed results and insights obtained here for doped ceria can be generalized and applied to other ion conductors that are important for SOFCs and SOECs as well as solid state batteries.

show abstract

Section: Introductionmentioning

confidence: 99%

Understanding the ionic conductivity maximum in doped ceria: trapping and blocking

Koettgen

Grieshammer

Hein

et al. 2018

Phys. Chem. Chem. Phys.

139

178

View full text Add to dashboard Cite

show abstract

“…Large solubilities above x = 0.3 have been reported for Sm, Yb, and Gd doped ceria. − Under oxygen-poor conditions, ceria can be reduced. This leads to the formation of polarons. , Several theoretical studies investigate this subject. − In this work, simulations are restricted to conditions were the electronic conductivity is significantly smaller than the ionic conductivity and thus is negligible.…”

Section: Theorymentioning

confidence: 99%

The Effect of Jump Attempt Frequencies on the Ionic Conductivity of Doped Ceria

Koettgen

Martin

2019

J. Phys. Chem. C

View full text Add to dashboard Cite

The macroscopic oxygen ion conductivity in doped ceria is determined by the microscopic activation energy barriers and jump attempt frequencies of oxygen ion jumps. While the influence of the local jump environment on the migration energy is widely investigated, its influence on the attempt frequency is rarely investigated. In this work, attempt frequencies in Sm, Yb, and Gd doped ceria are calculated using density functional theory. Moreover, ionic conductivities for varying local jump attempt frequencies in different jump environments are investigated using Kinetic Monte Carlo simulations. For doping along the migration pathway, where the migrating oxygen ion passes between two adjacent cations, large dopants lead to an increase and small dopants to a decrease in the attempt frequency. Sm doping in nearest neighborhood to the start position of the migrating oxygen vacancy also leads to an increase in attempt frequency. Kinetic Monte Carlo simulations show that at intermediate Sm dopant fractions oxygen vacancies frequently jump toward and away from dopants explaining why for Sm doped ceria one of the highest conductivities for a ternary cerium oxide was measured due to its low dopant-oxygen vacancy association in both nearest and next-nearest neighborhood.

show abstract

First Principles Study of Oxygen Incorporation Reactions in Oxides

Cited by 2 publications

References 40 publications

Understanding the ionic conductivity maximum in doped ceria: trapping and blocking

Understanding the ionic conductivity maximum in doped ceria: trapping and blocking

The Effect of Jump Attempt Frequencies on the Ionic Conductivity of Doped Ceria

Contact Info

Product

Resources

About