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Among their numerous technological applications, semi-coherent oxide heterostructures have emerged as promising candidates for applications in intermediate temperature solid oxide fuel cell electrolytes, wherein interfaces influence ionic transport.Since misfit dislocations impact ionic transport in these materials, oxygen vacancy formation and migration at misfit dislocations in oxide heterostructures are central to their performance as an ionic conductor. Herein, we report high-throughput atomistic simulations to predict thousands of activation energy barriers for oxygen vacancy migration at misfit dislocations in SrTiO3/BaZrO3 heterostructures. Dopants display a noticeable effect as higher activation energies are uncovered in their vicinity. Interface layer chemistry has a fundamental influence on the magnitude of activation energy barriers since they are dissimilar at misfit dislocations as compared to coherent terraces. Lower activation energies are uncovered when oxygen vacancies migrate toward misfit dislocations, but higher energies when they hop away, revealing that oxygen vacancies would get trapped at misfit dislocations and impact ionic transport. The results herein offer atomic scale insights into ionic transport at misfit dislocations and fundamental factors governing the ionic conductivity of thin film oxide electrolytes.
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Influence of misfit dislocations on ionic conductivity at oxide interfaces
Mismatched complex oxide thin films and heterostructures have gained significant traction for use as electrolytes in intermediate temperature solid oxide fuel cells, wherein interfaces exhibit variation in ionic conductivity as compared to the bulk. Although misfit dislocations present at interfaces in these structures impact ionic conductivity, the fundamental mechanisms responsible for this effect are not well understood. To this end, a kinetic lattice Monte Carlo (KLMC) model was developed to trace oxygen vacancy diffusion at misfit dislocations in SrTiO3/BaZrO3 heterostructures and elucidate the atomistic mechanisms governing ionic diffusion at oxide interfaces. The KLMC model utilized oxygen vacancy migration energy barriers computed using molecular statics. While some interfaces promote oxygen vacancy diffusion, others impede their transport. Fundamental factors such as interface layer chemistry, misfit dislocation structure, and starting and ending sites of migrating ions play a crucial role in oxygen diffusivity. Molecular dynamics (MD) simulations were further performed to support qualitative trends for oxygen vacancy diffusion. Overall, the agreement between KLMC and MD is quite good, though MD tends to predict slightly higher conductivities, perhaps a reflection of nuanced structural relaxations that are not captured by KLMC. The current framework comprising KLMC modeling integrated with molecular statics offers a powerful tool to perform mechanistic studies focused on ionic transport in thin film oxide electrolytes and facilitate their rational design.
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- Award ID(s):
- 2042311
- PAR ID:
- 10534843
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 12
- Issue:
- 32
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 21252 to 21267
- Subject(s) / Keyword(s):
- Thin film oxide electrolytes Ionic conductivity Kinetic Lattice Monte Carlo modeling Molecular dynamics Misfit dislocations Oxide interfaces
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1039/D4TA02034K
