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

Caige Liu, Shuangfeng Wu, Changzhi Yin, Jungu Xu*, Ying Xiong, Laijun Liu*, Jibran Khaliq, Chunchun Li*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Article number161259
Number of pages6
JournalJournal of Alloys and Compounds
Volume886
Early online date21 Jul 2021
DOIs
Publication statusE-pub ahead of print - 21 Jul 2021

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