Effects of crytals preferential orientation on phases quantitative analysis by Rietveld method

Rietveld method applied to XRD patterns is widely used for phase structure refinement or quantitative analysis. The equation giving the calculated intensity Ical of the simulated pattern shows that Ical is related to the scale intensity factor Sj of each phase, so it can give access to the quantitative analysis of weight fraction fj. However, the preferential orientation of crystals modifies the relative intensities of diffraction peaks, which may affect Sj and consequently the calculated weight fraction fj. The correction of this effect is taken into account throughout the Pkj factor, which is given by the March Dollase equation in Bragg Brentano symmetry.
In our work, we have studied the effect of the preferential orientation of (00l) planes of platelets shaped α-Al2O3 particles on quantitative analysis in MAUD. To reach our objective, mixtures of rounded shaped SiO2 particles with rounded or platelets shaped α-Al2O3 particles have been prepared and analyzed by XRD and then, by Rietveld method in MAUD. Two configurations were investigated for the specimen conditioning prior to XRD: free powder in the holder and pellets pressed at 100Mpa.
Weight fraction fj calculated by considering Pkj have been compared to those obtained without Pkj. The difference between calculated weight fractions is about 6-8%.