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- Title
Physically driven enhancement of the stability of Bi<sub>2</sub>O<sub>3</sub>-based ionic conductors via grain boundary engineering.
- Authors
Jeong, Incheol; Jeong, Seung Jin; Yun, Byung-Hyun; Lee, Jong-Won; Lee, Chan-Woo; Jung, WooChul; Lee, Kang Taek
- Abstract
Fast oxygen-ion conductors for use as electrolyte materials have been sought for energy conversion and storage. Bi2O3-based ionic conductors that exhibit the highest known oxygen-ion conductivities have received attention for use in next-generation solid electrolytes. However, at intermediate temperatures below ~600 °C, their conductivities degrade rapidly owing to a cubic-to-rhombohedral phase transformation. Here, we demonstrate that physical manipulation of the grain structure can be used to preserve the superior ionic conductivity of Bi2O3. To investigate the effects of microstructural control on stability, epitaxial and nanopolycrystalline model films of Er0.25Bi0.75O1.5 were fabricated by pulsed laser deposition. Interestingly, in situ impedance and ex situ XRD analyses showed that the grain boundary-free epitaxial film significantly improved the stability of the cubic phase, while severe degradation was observed in the conductivity of its polycrystalline counterpart. Consistently, the cation interdiffusion coefficient measured by the Boltzmann–Matano method was much lower for the epitaxial thin film compared to the polycrystalline thin film. Furthermore, first-principles calculations revealed that the presence of grain boundaries triggered the structural resemblance between cubic and rhombohedral phases, as evidenced by radial distribution functions. Additionally, phase transition energetics predicted that the thermodynamic stability of the cubic phase with respect to the rhombohedral counterpart is reduced near grain boundaries. Thus, these findings provide novel insights into the development of highly durable superionic conductors via microstructural engineering.We, for the first time, reveal that manipulation of microstructure enables the suppression of phase transformation and enhancement of long-term stability of Bi2O3-based ionic conductors. To investigate the microstructural influence on the stability, thin films with precisely defined grain structures are prepared. The conductivity of polycrystalline thin film decreased by 94.6% after approximately 20 h of operation, while the initial conductivity of epitaxial thin film remained almost constant during annealing for up to 100 h. This study provides novel insights for the development of highly conductive and durable solid electrolytes for next-generation energy applications.
- Publication
NPG Asia Materials, 2022, Vol 14, Issue 1, p1
- ISSN
1884-4049
- Publication type
Article
- DOI
10.1038/s41427-022-00402-7