铁电体SrBi_2Nb_2O_9电子能带结构的第一性原理研究  

Electronic band structure of ferroelectric SrBi_2Nb_2O_9

作　　者：唐春红[1,2] 蔡孟秋[1] 尹真[1] 张明生[1] 

机构地区：[1]南京大学物理系,固体微结构实验室,材料分析中心 [2]南京工程学院基础部,南京210013

出　　处：《物理学报》2004年第9期2931-2936,共6页Acta Physica Sinica

基　　金：国家自然科学基金 (批准号 :10 1740 3 4;10 3 740 47);江苏省自然科学基金 (批准号 :BK2 0 0 10 2 6)资助的课题~~

摘　　要：采用第一性原理的方法计算了SrBi2 Nb2 O9(SBN)的顺电相、铁电相的电子结构 .顺电相是间接带隙 ,铁电相是直接带隙 ,它们的大小分别为 1 5 7和 2 2 3eV .顺电相和铁电相的价带顶均主要来自于O2p态的贡献 .而顺电相和铁电相的导带底则分别来自Nb 4d态和Bi6p态的贡献 .计算表明SBN铁电相的低的漏电流与Bi6p轨道有关 .由顺电相到铁电相时 ,Nb 4d和O 2p轨道的强的杂化以及部分的Bi O (2 )杂化间接地增强NbO6 八面体的畸变 ,降低了体系的总能量 。The electronic band structures of SrBi 2Nb 2O 9 (SBN) in both the ferroelectric and paraelectric phases were calculated using first principles method. The paraelectric phase is of an indirect band gap of 1 57eV ; whereas the ferroelectric phase is of a direct band gap of 2 23eV. The valence band maxima of both the paraelectric and ferroelectric phases are mainly contributed from O2p states; while the conduction band minima are from Nb 4d and Bi 6p states. When transforming from the paraelectric to the ferroelectric phases, the strong hybridization between Nb 4d and O 2p and Bi O(2) hybridization enhance the distortion of NbO 6 octahedra and reduce the total energy of the system,in favor of stabilizing the ferroelectric phase. The calculation shows that the low leak current in SBN is related to Bi 6p state.

关 键 词：铁电材料 顺电相 铁电相 态密度 电子能带结构 

分 类 号：O482[理学—固体物理]