A proposed model for particle‐size effects in the X‐ray fluorescence analysis of heterogeneous powders that includes incidence angle and non‐random packing effects

An empirical model that includes the effect of incidence and exit angles and non‐random packing effects is proposed for describing the effect of particle size on the measured X‐ray fluorescence (XRF) response from thick heterogeneous samples. An exact model is derived that illustrates these effects for the ideal case of reglarly oriented cubes, and the previous models at high concentrations of a single homogeneous particale the proposed model and the previous models at high concentrations of a single homogeneous particle type where the largest difference between the previous models is observed. It is shown that at specific angles of incidence and exit the proposed model agrees closely with each of the earlier models. Experimental data taken at different incidence angles show that the proposed model provides the best least‐squares fit to the observed data on the basis of the minimum reduced chi‐square value.