Batuk Dmitry, Tsirlin Alexander A, Filimonov Dmitry S, Zakharov Konstantin V, Volkova Olga S, Vasiliev Alexander, Hadermann Joke, Abakumov Artem M
Electron Microscopy for Material Science (EMAT), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg , 86159 Augsburg, Germany.
Inorg Chem. 2016 Feb 1;55(3):1245-57. doi: 10.1021/acs.inorgchem.5b02465. Epub 2016 Jan 8.
The n = 3-6 members of a new perovskite-based homologous series Bi(3n+1)Ti7Fe(3n-3)O(9n+11) are reported. The crystal structure of the n = 3 Bi10Ti7Fe6O38 member is refined using a combination of X-ray and neutron powder diffraction data (a = 11.8511(2) Å, b = 3.85076(4) Å, c = 33.0722(6) Å, S.G. Immm), unveiling the partially ordered distribution of Ti(4+) and Fe(3+) cations and indicating the presence of static random displacements of the Bi and O atoms. All Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures are composed of perovskite blocks separated by translational interfaces parallel to the (001)p perovskite planes. The thickness of the perovskite blocks increases with n, while the atomic arrangement at the interfaces remains the same. The interfaces comprise chains of double edge-sharing (Fe,Ti)O6 octahedra connected to the octahedra of the perovskite blocks by sharing edges and corners. This configuration shifts the adjacent perovskite blocks relative to each other over a vector ½[110]p and creates S-shaped tunnels along the [010] direction. The tunnels accommodate double columns of the Bi(3+) cations, which stabilize the interfaces owing to the stereochemical activity of their lone electron pairs. The Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures can be formally considered either as intergrowths of perovskite modules and polysynthetically twinned modules of the Bi2Ti4O11 structure or as intergrowths of the 2D perovskite and 1D anatase fragments. Transmission electron microscopy (TEM) on Bi10Ti7Fe6O38 reveals that static atomic displacements of Bi and O inside the perovskite blocks are not completely random; they are cooperative, yet only short-range ordered. According to TEM, the interfaces can be laterally shifted with respect to each other over ±1/3a, introducing an additional degree of disorder. Bi10Ti7Fe6O38 is paramagnetic in the 1.5-1000 K temperature range due to dilution of the magnetic Fe(3+) cations with nonmagnetic Ti(4+). The n = 3, 4 compounds demonstrate a high dielectric constant of 70-165 at room temperature.
报道了基于钙钛矿的新同系物系列Bi(3n + 1)Ti7Fe(3n - 3)O(9n + 11)中n = 3 - 6的成员。利用X射线和中子粉末衍射数据（a = 11.8511(2) Å，b = 3.85076(4) Å，c = 33.0722(6) Å，空间群Immm）对n = 3的Bi10Ti7Fe6O38成员的晶体结构进行了精修，揭示了Ti(4+)和Fe(3+)阳离子的部分有序分布，并表明存在Bi和O原子的静态随机位移。所有Bi(3n + 1)Ti7Fe(3n - 3)O(9n + 11)结构均由平行于(001)p钙钛矿平面的平移界面分隔的钙钛矿块组成。钙钛矿块的厚度随n增加，而界面处的原子排列保持不变。界面由双边共享(Fe,Ti)O6八面体链组成，这些八面体通过共享边和角与钙钛矿块的八面体相连。这种构型使相邻的钙钛矿块相对于彼此在向量½[110]p上发生位移，并沿[010]方向形成S形隧道。隧道容纳Bi(3+)阳离子的双列，由于其孤电子对的立体化学活性，这些阳离子使界面稳定。Bi(3n + 1)Ti7Fe(3n - 3)O(9n + 11)结构可以形式上被视为钙钛矿模块和Bi2Ti4O11结构的多晶孪晶模块的共生体，或者视为二维钙钛矿和一维锐钛矿片段的共生体。对Bi10Ti7Fe6O38的透射电子显微镜（TEM）研究表明，钙钛矿块内Bi和O的静态原子位移并非完全随机；它们是协同的，但只是短程有序。根据TEM，界面可以相对于彼此在±1/3a范围内横向移动，引入了额外的无序度。由于磁性Fe(3+)阳离子被非磁性Ti(4+)稀释，Bi10Ti7Fe6O38在1.5 - 1000 K温度范围内是顺磁性的。n = 3、4的化合物在室温下表现出70 - 165的高介电常数。
