钛酸钡纳米颗粒聚集球的形成机理

摘要

A novel nanoparticle aggregation structure of barium titanate was obtained by the hydrothermal method. Powder X-ray diffraction (XRD) revealed that the aggregates crystallized in the cubic phase. The crystallization of the products became more significant with reaction progress. The growth characteristics of the aggregates was further confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and electron diffraction (ED) spectroscopy. The aggregation was composed of many 5-8 nm nanoparticles by orientation attachment and we found that the ED patterns indicated a single-crystal property for the aggregates. The size of the aggregates was about 60 nm and they grew as the reaction continued. From the results of energy dispersive X-ray (EDX) spectroscopy analysis and kinetics modeling using the Johnson-Mehl-Avrami (JMA) equation, the diffusion nucleation of Ba2* ion was found to be dominant during the early stages of aggregation formation. The growth process of "diffusion nucleation-orientation attachment" revealed the formation mechanism of barium titanate nanoparticle aggregations.%采用水热法合成了具有新颖结构的钛酸钡纳米颗粒聚集球.X射线衍射(XRD)结果显示该聚集球为立方相,随着时间的延长其结晶性增强.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)和电子衍射(ED)谱研究了该纳米颗粒聚集球的生长特点.结果表明该聚集球是由5-8 nm的纳米颗粒定向连接生长而成,整个聚集球对外显示类单晶的现象.聚集球的大小约为60 nm,随着时间的延长有长大的趋势.X射线能谱(EDX)分析结果和Johnson-Mehl-Avrami (JMA)方程动力学模拟结果表明,在颗粒球形成初始阶段主要是Ba2+离子的扩散成核作用占主导地位.这种"扩散成核-定向生长"的形成过程揭示了钛酸钡纳米颗粒聚集球的生长机理.