利用透射电子显微技术及理论模拟研究BiMnO3的结构  

STRUCTURES OF BiMnO_3 STUDIED BY A TRANSMISSION-ELECTRON MICROSCOPY AND THEORETICAL SIMULATIONS

作　　者：杨华[1,2] 县涛[2] 迟振华[3] 

机构地区：[1]兰州理工大学,甘肃省有色金属新材料省部共建国家重点实验室,兰州730050 [2]兰州理工大学理学院,兰州730050 [3]中国科学院物理研究所、北京凝聚态物理国家实验室,北京100190

出　　处：《硅酸盐学报》2009年第6期1000-1004,共5页Journal of The Chinese Ceramic Society

基　　金：兰州理工大学博士基金(SB10200701);甘肃省教育厅科研(0703B-1)资助项目。

摘　　要：在高压下合成BiMnO_3陶瓷样品,利用透射电子显微技术及理论模拟系统研究其室温结构。电子衍射数据表明:BiMnO_3形成的是中心对称的C2/c结构,而不是非中心对称的C2结构,该结果通过电子衍射花样和高分辨电子显微像的模拟计算得到进一步证实。此外,在样品中还观察到一种体心赝立方超点阵相,点阵参数为4a_p×4b_p×4c_p。电子能量损失谱和能量散射X射线谱成分分析结果表明:在超点阵相中缺失了部分氧原子。通过高分辨像模拟,揭示了超点阵的形成是由于有序氧缺位所致。按照晶体学观点认为:在BiMnO_3中测得的弱铁电极化起源于这种超点阵。A BiMnO3 ceramic sample was synthesized under high pressure, and the transmission electron microscope and theoretical simulations were used to characterize its room-temperature structures. The electron diffraction data revealed that the stoichiometric BiMnO3 crystallizes in the centrosymmetric C2/c structure, not in the noncentrosymmetric C2 structure. This is confirmed by further calculations of the electron diffraction patterns and high-resolution transmission electron microscope（HRTEM） photographs. A second polymorph, characterized as a body-centered pseudocubic superstructure with the lattice constants of 4ap×4bp×4Cp, is also found in the present sample. Composition analyses using electron energy-loss spectroscopy and energy dispersive X-ray show a slight loss of oxygen atoms in the superlattice phase.The HRTEM photographs simulations reveal that the superlattice is formed as the result of an ordered oxygen deficiency. In terms of crystallography, the weak ferroelectric polarizations measured in the BiMnO3 samples originate from the superlattice are suggested.

关 键 词：锰酸铋 多铁性 晶体结构 超点阵 透射电子显微学 理论模拟 

分 类 号：O469[理学—凝聚态物理]