Precise calculation of crystallite size of nanomaterials: A review

Crystallite size has an important effect on the chemical, physical and mechanical properties of metallic, polymeric, and ceramic nanomaterial. Therefore, finding a reliable method to calculate the crystallite size has been a hot debate in recent decades. Many direct and indirect measurement methods have been proposed. However, findings showed that some of them are reliable while others do not provide a good approximation. In the present review, a comprehensive study has been made to investigate these techniques, which are mainly based on X-Ray diffraction, Raman spectroscopy, and dark-field transmission electron microscopy. Scherrer method has been widely used as the easiest and fastest route to calculate crystallite size. However, most of the methods based on the peak broadening of XRD do not give information about the crystallite size distribution. In addition, some calculational and technical errors reduce the accuracy of measurement which should be corrected. Raman spectroscopy is also a suitable method that gives relatively accurate results. Although this method has been well documented for carbon-based nanomaterial, there are still some computational difficulties for the other nanosystems. An effective way for precise calculation of crystallite size is dark field TEM/HRTEM which provides both crystallite size and crystallite size distribution. However, this method provides information from a small area of surface, which is not representative of the entire sample. Therefore, due to the limitations of each method, a combination of these techniques may provide complimentary results which is the best strategy for an in-depth analysis of crystallite size, lattice strain and crystallite size distribution.