Ratio of slopes method for quantitative X-ray diffraction analysis

Abstract

This method, which employs an internal standard, is both easy to use and accurate. The required weight fraction of a phase in the mixture to be analysed is determined from the ratio of slopes of two linear plots passing through their respective origins, designated as the analysis and reference lines. The analysis line is obtained by plotting the intensity ratio of the required phase to the standard against the weight ratio of the mixture to the standard, for different proportions of mixture and standard. The reference line for the required phase is obtained by plotting the intensity ratio against the weight ratio of the reference material to the standard, using a pure phase or a reference material of known composition. The ease of use comes when weighing out the samples to be X-rayed. The weight of the mixture to be analysed, the reference material and the internal standard need not be any specific values or in any fixed proportions but, of course, require to be determined precisely. The weight ratios can be chosen so that peak intensities can be measured accurately. Precise weighing and the ability to use various weight ratios can give this method greater accuracy than that of the conventional internal standard method.