Crystal structure and the paraelectric-to-ferroelectric phase transition of nanoscale BaTiO3
Crystal structure and the paraelectric-to-ferroelectric phase transition of nanoscale BaTiO3
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DOI：
10.1021/ja0758436
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发表时间：
2008-06-04
影响因子：
15
通讯作者：
Steigerwald, Michael L.
中科院分区：
文献类型：
--
作者：
Smith, Millicent B.;Page, Katharine;Steigerwald, Michael L.
利用变温拉曼光谱和粉末X射线衍射（XRD）研究了不同尺寸纳米钛酸钡（BaTiO 3）的顺电-铁电相变。同步辐射X射线散射已被用来阐明不同尺寸的颗粒的室温结构，通过使用两个Rietveld细化和对分布函数（PDF）分析。我们观察到的铁电四相，即使是最小的颗粒在26 nm。通过使用温度依赖的拉曼光谱和XRD，我们发现，相变是扩散的温度为较小的颗粒，在对比的急剧转变，发现为散装样品。然而，实际转变温度几乎不变。Rietveld和PDF分析表明，随着颗粒尺寸的减小，畸变增加，尽管与立方平均结构的趋势相结合。这些结果表明，虽然结构畸变对颗粒尺寸的变化是鲁棒的，但受影响的是畸变的相干性，其在较小的颗粒中降低。
We have investigated the paraelectric-to-ferroelectric phase transition of various sizes of nanocrystalline barium titanate (BaTiO3) by using temperature-dependent Raman spectroscopy and powder X-ray diffraction (XRD). Synchrotron X-ray scattering has been used to elucidate the room temperature structures of particles of different sizes by using both Rietveld refinement and pair distribution function (PDF) analysis. We observe the ferroelectric tetragonal phase even for the smallest particles at 26 nm. By using temperature-dependent Raman spectroscopy and XRD, we find that the phase transition is diffuse in temperature for the smaller particles, in contrast to the sharp transition that is found for the bulk sample. However, the actual transition temperature is almost unchanged. Rietveld and PDF analyses suggest increased distortions with decreasing particle size, albeit in conjunction with a tendency to a cubic average structure. These results suggest that although structural distortions are robust to changes in particle size, what is affected is the coherency of the distortions, which is decreased in the smaller particles.