Phase transformation and ionic conductivity mechanism of a low-temperature sintering semiconductor Na2CaV4O12

Liu, Caige, Wu, Shuangfeng, Yin, Changzhi, Xu, Jungu, Xiong, Ying, Liu, Laijun, Khaliq, Jibran and Li, Chunchun (2021) Phase transformation and ionic conductivity mechanism of a low-temperature sintering semiconductor Na2CaV4O12. Journal of Alloys and Compounds, 886. p. 161259. ISSN 0925-8388

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Alkaline earth metal vanadates have drawn attention because of their potential applications in electrochemical devices. Here, Na2CaV4O12 was prepared at extremely low temperatures (350-550 oC) and showed a semiconductor behavior with a bandgap of 2.92 eV. A phase transition from P4/nbm to P
b2 occurred at 510 oC was identified by an in-situ XRD upon heating, where the 16 n site for oxygen atoms in the P4/nbm phase evolves into two distinguishable 8i sites in the P
b2 phase. Ionic conduction in Na2CaV4O12 at elevated temperatures was reported for the first time in the present work. A strong correlation between ionic conductivity and phase structure of Na2CaV4O12 is observed. The charged carriers are mainly sodium ions for the low-temperature P4/nbm phase, while mixed conduction contributed by sodium ions and oxide ions happened in the transformed phase. Bond valence-based energy landscape calculations disclosed a two-dimensional interstitial diffusion mechanism for Na+ ions in the Na2Ca-layers, as well as a two-dimensional diffusion mechanism for oxide ions in the V4O12-layers. The novel semiconductor ceramic would have potential applications in all-solid sodium ions batteries or solid oxide fuel cells as electrolytes.

Item Type: Article
Additional Information: Funding information: The authors gratefully acknowledge the financial support from the Natural Science Foundation of China (No. 62061011), Natural Science Foundation of Guangxi Zhuang Autonomous Region (No. 2018GXNSFAA281253, 2019GXNSFGA245006, 2019GXNSFBA245069, 2020GXNSFBA297029), the high-level innovation team and outstanding scholar program of Guangxi institutes, and Open Fund from Guangxi Key Laboratory of Optical and Electronic Materials and Devices (No. 20AA-4, 20AA-7).
Uncontrolled Keywords: Mixed-cation vanadate, Electrical conductivity, Dielectric properties, Ceramics
Subjects: H300 Mechanical Engineering
H800 Chemical, Process and Energy Engineering
H900 Others in Engineering
Department: Faculties > Engineering and Environment > Mechanical and Construction Engineering
Depositing User: Rachel Branson
Date Deposited: 22 Jul 2021 13:08
Last Modified: 21 Jul 2022 03:31

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