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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Crystal structure of Bi4-xCexTi3O12(x=0, 0.25, 0.5 and 0.75) studied by Raman spectroscopy and neutron powder diffraction
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Crystal structure of Bi4-xCexTi3O12(x=0, 0.25, 0.5 and 0.75) studied by Raman spectroscopy and neutron powder diffraction

机译：拉曼光谱和中子粉末衍射研究Bi4-xCexTi3O12（x = 0、0.25、0.5和0.75）的晶体结构

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摘要

Structural refinement using both neutron powder diffraction data and Raman spectroscopy were carried out to determine the site preference of Ce atoms and structural changes in Bi4-xCexTi3O12 (x=0, 0.25, 0.5 and 0.75) compounds. In the Raman spectroscopic study, the peak at 65 cm(-1) of Bi4Ti3O12 (BTO), assigned to the Bi-O bonds in the Bi2O2 layers, did not shift or shifted to 63 cm(-1) after Ce incorporation. However, the peaks of BTO at 119 and 148 cm(-1), assigned to the Bi-O bonds in the perovskite units, became diffusive and moved to higher frequencies of (121 and 150 cm(-1)), (123 and 152 cm(-1)) and (125 and 157 cm(-1)) when x was 0.25, 0.5 and 0.75, respectively. From the Raman spectroscopic study, the substitution sites of the Ce atoms were determined to be only the Bi sites in the perovskite units. The peaks originated from the TiO6 octahedrons moved to higher frequencies and merged with the neighbouring peaks, indicating relaxation of distortion of TiO6 octahedrons with increase in x. Structural refinement results showed that the a-axis lattice parameters decreased with increase in x, while the b-axis lattice parameters did not exhibit significant changes and the c-axis lattice parameters decreased. Decrease in orthorhombicity with increasing x showed the relaxation of structural distortion of TiO6 octahedrons. Spontaneous polarization was calculated based on the refinement results, which decreased from 35.4 to 30.4, 27.5 and 16.5 mu C cm(-2) when x is 0, 0.25, 0.5 and 0.75, respectively.
机译：使用中子粉末衍射数据和拉曼光谱进行结构改进，以确定Ce原子的位点偏爱和Bi4-xCexTi3O12（x = 0、0.25、0.5和0.75）化合物的结构变化。在拉曼光谱研究中，Bi4Ti3O12（BTO）在65 cm（-1）处的峰分配给Bi2O2层中的Bi-O键，在Ce掺入后没有移动或移至63 cm（-1）。但是，在钙钛矿单元中分配给Bi-O键的BTO的峰值在119和148 cm（-1）处变得扩散，并移至更高的频率（121和150 cm（-1）），（123和当x分别为0.25、0.5和0.75时约为152厘米（-1））和（125和157厘米（-1））。根据拉曼光谱研究，Ce原子的取代位点确定为仅钙钛矿单元中的Bi位点。源自TiO6八面体的峰移动到更高的频率并与相邻的峰合并，表明TiO6八面体的畸变随x的增加而松弛。结构细化结果表明，a轴晶格参数随x的增加而降低，而b轴晶格参数没有显着变化，而c轴晶格参数则降低。正交性随着x的增加而降低，表明TiO6八面体的结构变形得到缓和。根据细化结果计算自发极化，当x分别为0、0.25、0.5和0.75时，自发极化从35.4降至30.4、27.5和16.5μC cm（-2）。

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