Crystal structures and ferroelectric properties of SrBi2Ta2O9 and Sr0.8Bi2.2Ta2O9
Crystal structures and ferroelectric properties of SrBi2Ta2O9 and Sr0.8Bi2.2Ta2O9
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DOI：
10.1063/1.123708
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发表时间：
1999-03
影响因子：
4
通讯作者：
Y. Shimakawa;Y. Kubo;Y. Nakagawa;T. Kamiyama;H. Asano;F. Izumi
中科院分区：
文献类型：
--
作者：
Y. Shimakawa;Y. Kubo;Y. Nakagawa;T. Kamiyama;H. Asano;F. Izumi
用中子粉末衍射法对化学计量比的SrBi_2Ta_2O_9（TC=300 °C）和贫Sr富Bi的Sr_0.8Bi_2.2Ta_2O_9（TC=400 °C）的晶体结构进行了细化。Bi_2O_2层和TaO_6八面体发生明显的畸变，原子沿a轴沿着方向的位移引起铁电自发极化。在Sr0.8Bi2.2Ta2O9中，Bi取代和Sr位的阳离子空位都被揭示，并且获得了（Sr0.82Bi0.12）Bi2Ta2O9.0的化学组成。计算的极化的Sr0.8Bi2.2Ta2O9是大于化学计量样品，这是与观察到的薄膜电容器中的反射极化一致。Bi的替代和Sr位的阳离子空位增强了TaO6八面体的结构畸变，导致了更大的铁电自发极化和更高的居里温度。
Crystal structures of ferroelectric materials of stoichiometric SrBi2Ta2O9 (TC=300 °C) and Sr-deficient-and-Bi-excess Sr0.8Bi2.2Ta2O9 (TC=400 °C) were refined by neutron powder diffraction. Bi2O2 layer and TaO6 octahedra are considerably distorted and atomic displacements along the a axis cause ferroelectric spontaneous polarization. In Sr0.8Bi2.2Ta2O9, both Bi substitution and cation vacancies at the Sr site were revealed and a chemical composition of (Sr0.82Bi0.12)Bi2Ta2O9.0 was obtained. The calculated polarization of Sr0.8Bi2.2Ta2O9 is larger than that of the stoichiometric sample, which is consistent with observations of remanent polarization in thin-film capacitors. The Bi substitution and the cation vacancies at the Sr site enhance structural distortion in the TaO6 octahedra and lead to the larger ferroelectric spontaneous polarization and the higher Curie temperature.