Absorption contrast effects in the quantitative XRD analysis of powders by full multiphase profile refinement

It is shown that quantitative X-ray powder diffraction analyses using full profile multiphase refinement should include corrections for the Brindley particle absorption contrast effect. This is demonstrated with synthetic mixtures of the highly contrasting phases LiF and Pb(NO₃)₂ (μ/ρ = 20 and 231 cm⁻¹ for Co Kα). With contrast corrections, the only parameter which needs to be input is an effective particle radius R for each phase. For mixtures of LiF and Pb(NO₃)₂ over the whole composition range, quantification is achieved, under the present specimen preparation method, with an effective particle radius of 51 μm for both phases, giving analyses correct to within 1 percentage point. Without Brindley corrections, the analysis is grossly in error.