Open-source Rietveld refinement for cellulose crystallinity using a laboratory powder X-ray diffractometer: a hands-on tutorial

Accurate measurement of cellulose crystallinity is essential for understanding fiber development, optimizing processing conditions, and improving material performance. However, the structural complexity of cellulose fibers presents significant challenges in determining crystallinity, or more precisely, the ratio of two discrete crystalline and amorphous model phases. As a result, many studies rely on empirical methods to estimate a crystallinity index (CrI). This study presents a cellulose-specific workflow for quantifying crystallinity from one-dimensional X-ray powder diffraction (XRD) data using Rietveld refinement implemented in the open-source software MAUD. The step-by-step procedure—demonstrated using cotton fiber and tailored for non-specialists—guides users through refinement of ten key parameters, including a scale factor, background, unit cell geometry, crystallite size, preferred orientation, and phase composition, in four sequential refinement steps. The final refinement yielded strong agreement between calculated and observed diffraction patterns and demonstrated the utility of one-dimensional full-pattern analysis in a workflow to quantify cellulose crystallinity.