Journal of Inorganic Materials ›› 2014, Vol. 29 ›› Issue (1): 38-42.DOI: 10.3724/SP.J.1077.2014.12719

• Research Paper • Previous Articles     Next Articles

First-principles Study of Intergrowth Bismuth Layer-structured Ferroelectric Bi7Ti4NbO21

LIU Feng1, 2, LU Yi-Qing1, LI Yong-Xiang1   

  1. (1. The Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China)
  • Received:2012-12-03 Revised:2013-02-19 Published:2014-01-20 Online:2013-12-09
  • About author:LIU Feng.
  • Supported by:

    National Natural Science Foundation of China (50932007); Program of Shanghai Subject Chief Scientist (10XD1404700)

Abstract: Intergrowth bismuth layer-structured ferroelectric Bi7Ti4NbO21 material (iBTN) is a natural super lattice structure with excellent properties. Ferroelectric iBTN and parent compounds Bi3TiNbO9 (BTN) and Bi4Ti3O12 (BiT) were studied with first-principles method based on density functional theory (DFT). The band structures and the density of states of different compounds were calculated based on their optimized structures. The enthalpy of formation and band gaps of iBTN, BTN and BiT are -56.21, -30.72, -43.32 eV and 0.796, 2.535, 2.436 eV, respectively. The analysis shows that the intergrowth structure iBTN stays at a thermodynamic metastable state in relative to BTN and BiT. The electronic conductivity of iBTN is mainly depended on the perovskite layers, and the narrowed band gap is attributed to the down shift of the bottom of the conduction band. Detailed partial density of states of iBTN shows that different perovskite layers have different effects on the conduction band which suggests that the electrons choose their transportation channels in this material. This study can improve the understanding of the intergrowth mechanism and the influence between the structure and the electronic properties of iBTN.

Key words: Bi7Ti4NbO21, intergrowth bismuth layer-structured ferroelectric, first-principles, enthalpy of formation, band gap

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