Patra Soumitra, Satpati Biswarup, Pradhan Swapan Kumar
Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal, India.
J Nanosci Nanotechnol. 2011 Jun;11(6):4771-80. doi: 10.1166/jnn.2011.3927.
CdS quantum dots (QDs) with a mixture of both cubic (Zinc-blende) and hexagonal (Wurtzite) phases have been prepared within 50 min by mechanical alloying the stoichiometric mixture of Cd and S powders at room temperature in a planetary ball mill under Ar. The Rietveld analysis of X-ray powder diffraction data collected from ball-milled samples estimates relative phase abundances of cubic and hexagonal phases and several microstructure parameters like lattice parameters, particle size, lattice strain, concentrations of different kinds of stacking faults etc. in both kinds of QDs. Initially, the hexagonal phase is formed and then simultaneously, the most dense plane (111) of minor cubic phase is formed coherently on the most dense (002) plane of hexagonal phase. In the course of milling up to 30 h, the hexagonal phase partially transforms slowly to cubic phase and the molar ratio of cubic and hexagonal phase becomes approximately 0.7:0.3 and particles sizes of both phases reduce to approximately 6 nm. The cubic phase contains a significant amount of lattice strain but the hexagonal phase is almost strain-free. The presence of different kinds of stacking faults is revealed clearly from the high resolution transmission electron microscope (HRTEM) images. The particle sizes of QDs and their distributions obtained from the Rietveld analysis agree well with the analysis of HRTEM images.
通过在室温下于氩气氛围中的行星式球磨机内对化学计量比的镉粉和硫粉混合物进行机械合金化处理，在50分钟内制备出了具有立方（闪锌矿）和六方（纤锌矿）混合相的硫化镉量子点（QDs）。对球磨样品收集的X射线粉末衍射数据进行的Rietveld分析估算了两种量子点中立方相和六方相的相对相丰度以及几个微观结构参数，如晶格参数、粒径、晶格应变、不同类型堆垛层错的浓度等。最初，形成六方相，然后同时在六方相的最密排（002）面上相干地形成少量立方相的最密排面（111）。在球磨长达30小时的过程中，六方相缓慢地部分转变为立方相，立方相和六方相的摩尔比变为约0.7:0.3，且两相的粒径均减小至约6纳米。立方相含有大量晶格应变，但六方相几乎无应变。从高分辨率透射电子显微镜（HRTEM）图像中可以清楚地看出不同类型堆垛层错的存在。从Rietveld分析获得的量子点粒径及其分布与HRTEM图像分析结果吻合良好。
