Experimental Study of Effect of Crystallite Size Statistics on X-Ray Diffractometer Intensities

Abstract

The relative rms deviation σ of the intensity of a rapidly rotating polycrystallite specimen is σ=[6.5R sinθ]/[h(mNeff)½], where R=goniometer radius, θ=Bragg angle, h=(hf+hs)/2, hf=length of focal spot, hs=length of receiving slit, m=multiplicity factor, and Neff the effective number of irradiated crystallites. Experimental data on silicon powder specimens are presented to show the dependence of σ on crystallite sizes, choice of x-ray wavelengths and various other experimental parameters. Comparisons of data for rapidly rotating and stationary specimens having crystallite sizes in the 30–50 μ range show that rotation improves σ by a factor of 7 or 8 for peak intensities and 4 or 5 for integrated intensities, using a standard diffractometer.