Crystallite Size Analysis with XRDynamic 500
X-ray diffraction was used to analyze crystallite size and peak broadening in nanocrystalline materials. Instrumental broadening was determined using SRM 660c LaB₆ and applied to the analysis of SRM 1979 ZnO powders with nominal sizes of 15 nm and 60 nm. Measurements performed with a monochromator showed reduced background noise and improved peak intensity compared to a Kβ filter. Crystallite sizes were reliably determined by Rietveld refinement incorporating instrumental broadening, whereas the Scherrer equation overestimated crystallite size due to neglecting additional sources of errors.
Introduction
X-ray diffraction (XRD) is a widely used technique to investigate the structural properties of crystalline materials. One of the key parameters that can be determined from XRD data is the crystallite size, which refers to the size of coherently diffracting domains within a material. Crystallite size and strain significantly influence the physical properties of materials, including their mechanical, electrical, magnetic, and optical behavior. Therefore, accurately quantifying size and strain along with understanding the relationship between them is essential in the field of materials science.
The broadening of diffraction peaks in an XRD pattern provides information about the crystallite size. According to the Scherrer equation, a long-established and widely used method, the width of diffraction peaks increases as the crystallite size decreases due to the limited number of lattice planes contributing to the diffraction.
The Scherrer equation is expressed as: D=(K λ)/(β cosθ)
where D is the average crystallite size, K is the shape factor (typically around 0.9), λ is the wavelength of the X ray source, β is the full width at half maximum (FWHM) of the diffraction peak (in radians), and θ is the Bragg angle.
By applying this relation to the experimental XRD data, the average crystallite size can be estimated. However, it is important to note that peak broadening also arises from lattice strain and instrumental effects, so appropriate corrections or complementary analyses may be necessary for accurate results.
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