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δ-Bi 2 O 3 has long been touted as a potential material for use in solid oxide fuel cells (SOFC) due to its intrinsically high ionic conductivity. However, its limited operational temperature has led to stabilising the phase from >725 °C to room temperature either by doping, albeit with a compromise in conductivity, or by growing the phase confined within superlattice thin films. Superlattice architectures are challenging to implement in functional μSOFC devices owing to their ionic conducting channels being in the plane of the film. Vertically aligned nanocomposites (VANs) have the potential to overcome these limitations, as their nanocolumnar structures are perpendicular to the plane of the film, hence connecting the electrodes at top and bottom. Here, we demonstrate for the first time the growth of epitaxially stabilised δ-Bi 2 O 3 in VAN films, stabilised independently of substrate strain. The phase is doped with Dy and is formed in a VAN film which incorporates DyMnO 3 as a vertically epitaxially stabilising matrix phase. Our VAN films exhibit very high ionic conductivity, reaching 10 −3 S cm −1 at 500 °C. This work opens up the possibility to incorporate thin film δ-Bi 2 O 3 based VANs into functional μSOFC devices, either as cathodes (by pairing δ-Bi 2 O 3 with a catalytically active electronic conductor) and/or electrolytes (by incorporating δ-Bi 2 O 3 with an insulator).
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Spontaneous Ordering of Oxide-Oxide Epitaxial Vertically Aligned Nanocomposite Thin Films
The emerging field of self-assembled vertically aligned nanocomposite (VAN) thin films effectively enables strain, interface, and microstructure engineering as well as (multi)functional improvements in electric, magnetic, optical, and energy-related properties. Well-ordered or patterned microstructures not only empower VAN thin films with many new functionalities but also enable VAN thin films to be used in nanoscale devices. Comparative ordered devices formed via templating methods suffer from critical drawbacks of processing complexity and potential contamination. Therefore, VAN thin films with spontaneous ordering stand out and display many appealing features for next-generation technological devices, such as electronics, optoelectronics, ultrahigh-density memory systems, photonics, and 3D microbatteries. The spontaneous ordering described in this review contains ordered/patterned structures in both in-plane and out-of-plane directions. In particular, approaches to obtaining spontaneously ordered/patterned structures in-plane are systematically reviewedfrom both thermodynamic and kinetic perspectives. Out-of-plane ordering is also discussed in detail. In addition to reviewing the progress of VAN films with spontaneous ordering, this article also highlights some recent developments in spontaneous ordering approaches and proposes future directions.
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- PAR ID:
- 10227049
- Date Published:
- Journal Name:
- Annual Review of Materials Research
- Volume:
- 50
- Issue:
- 1
- ISSN:
- 1531-7331
- Page Range / eLocation ID:
- 229 to 253
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1146/annurev-matsci-091719-112806
