Size effect on the crystal structure of barium titanate nanoparticles
Size effect on the crystal structure of barium titanate nanoparticles
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DOI：
10.1063/1.1935132
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发表时间：
2005-07
影响因子：
3.2
通讯作者：
M. Yashima;T. Hoshina;Daiju Ishimura;Syuuhei Kobayashi;Wataru Nakamura;T. Tsurumi;S. Wada
中科院分区：
文献类型：
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作者：
M. Yashima;T. Hoshina;Daiju Ishimura;Syuuhei Kobayashi;Wataru Nakamura;T. Tsurumi;S. Wada
利用中子和高分辨率同步x射线粉末衍射和拉曼散射技术，研究了40、140和430纳米尺寸的钛酸钡（BaTiO3）纳米颗粒的晶体结构。这些样品是由草酸钛钡采用改进的两步热分解法制得的，晶格杂质很少。对430 nm和140 nm尺寸的BaTiO3粒子的中子衍射数据进行了Rietveld分析，假设其为单相四方（P4mm）结构。在430 ~ 140 nm范围内，BaTiO3的轴向比c / a随粒径的减小而减小。尺寸为40 nm的钛酸钡颗粒由(1)四方晶（83 wt %）和(2)六方晶（P63mmc, 17 wt %）组成，前者具有较大的晶胞体积，轴向比为单位c / a=1.000(5)。Rietveld和最大熵方法分析表明，存在原子位移，偏离了理想位置。
A size effect on crystal structure has been investigated for barium titanate (BaTiO3) nanoparticles of 40-, 140-, and 430-nm sizes, by means of neutron and high-resolution synchrotron x-ray powder-diffraction and Raman-scattering techniques. These samples were prepared by a modified two-step thermal decomposition method from barium titanyl oxalate, resulting in very few lattice impurities. Rietveld analysis of the neutron-diffraction data for the 430-nm- and 140-nm-sized BaTiO3 particles was performed assuming a single phase of tetragonal (P4mm) structure. The axial ratio c∕a of tetragonal BaTiO3 decreases with a decrease in particle size from 430 to 140 nm. Barium titanate particles with a size of 40 nm consist of (1) tetragonal crystals (83 wt %) with a large cell volume and an axial ratio of unity c∕a=1.000(5) and of (2) a hexagonal phase (P63mmc, 17 wt %) with a large unit-cell volume. Rietveld and maximum-entropy method analyses suggest that there exist atomic displacements from the ideal site of a c...