Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
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DOI：
10.3938/jkps.51.878
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发表时间：
2007-08
影响因子：
0.6
通讯作者：
S. Wada;T. Hoshina;K. Takizawa;Masanori Ohishi;Hiroaki Yasuno;H. Kakemoto;T. Tsurumi;C. Moriyoshi;Y. Kuroiwa
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文献类型：
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作者：
S. Wada;T. Hoshina;K. Takizawa;Masanori Ohishi;Hiroaki Yasuno;H. Kakemoto;T. Tsurumi;C. Moriyoshi;Y. Kuroiwa
采用草酸氧钛钡在不同真空度下的两步热分解法制备了粒径为17~1000 nm的钛酸钡（BaTiO3）纳米颗粒。各种表征表明这些颗粒是无杂质、无缺陷、致密的 BaTiO3 纳米颗粒。当真空度较高时（压力为150 Pa，温度为650℃），尺寸约为60 nm的BaTiO3颗粒的介电常数最大，约为15,000。另一方面，当真空度较低时（650℃、压力为 400 Pa），没有观察到介电最大值。为了解释这种尺寸依赖性，我们使用同步加速器辐射精确研究了粒子结构。结果，颗粒始终由两层组成，即表面立方层和本体四方层，并且在BaTiO3纳米粒子的制备过程中，表面立方层的厚度随着真空度的增加而减小。因此，我们证实表面结构是决定 BaTiO3 纳米颗粒介电性能的重要因素。
Barium titanate (BaTiO3) nanoparticles with various particle sizes from 17 to 1,000 nm were prepared by using the 2-step thermal decomposition method of barium titanyl oxalate under various degree of vacuum. Various characterizations revealed that these particles were impurity-free, defectfree, dense BaTiO3 nanoparticles. When the degree of vacuum was high (pressure of 150 Pa at 650 ◦C), the dielectric constant of BaTiO3 particles with a size of around 60 nm exhibited a maximum of around 15,000. On the other hand, when the degree of vacuum was low (pressure of 400 Pa at 650 ◦C), no dielectric maximum was observed. To explain this size dependence, we precisely investigated a particle structure by using synchrotron radiation. As a result, the particles were always composed of two layers, i.e., a surface cubic layer and a bulk tetragonal layer, and the thickness of the surface cubic layer decreased with increasing degree of vacuum during the preparation of BaTiO3 nanoparticles. Thus, we confirmed that the surface structure was an important factor in determining the dielectric properties of BaTiO3 nanoparticles.