铋层状共生结构铁电体Bi_7Ti_4NbO_(21)的第一性原理计算  

First-principles Study of Intergrowth Bismuth Layer-structured Ferroelectric Bi_7Ti_4NbO_(21)

作　　者：刘峰[1,2] 陆毅青[1] 李永祥[1] 

机构地区：[1]中国科学院上海硅酸盐研究所,无机功能材料与器件重点实验室,上海200050 [2]中国科学院大学,北京100049

出　　处：《无机材料学报》2014年第1期38-42,共5页Journal of Inorganic Materials

基　　金：国家自然科学基金重点项目(50932007);上海市优秀学科带头人(10XD1404700)~~

摘　　要：铋层状共生结构铁电体Bi7Ti4NbO21具有天然的超晶格结构。采用基于密度泛函(DFT)的第一性原理计算对Bi7Ti4NbO21及其相关化合物进行了研究。计算得到Bi7Ti4NbO21的生成焓为-56.21 eV,带隙为0.796 eV,而对于组成单元Bi3TiNbO9和Bi4Ti3O12,生成焓分别为-30.72和-43.32 eV,带隙分别为2.535和2.436 eV。分析表明,共生结构Bi7Ti4NbO21相对于同组分的组成单元处于热力学亚稳态,其钙钛矿层是电子电导的主要影响因素,带隙相对于组成单元减小也是源于钙钛矿层的导带底的下移。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.

关 键 词：Bi7Ti4NbO21 共生结构铁电体 第一性原理 生成焓 带隙 

分 类 号：TQ174[化学工程—陶瓷工业]