XING Chao-gang, YUAN Jing-qun, QI Dong-mei, WANG Jiao-jiao, LV Guang-lie, LI Shi-min*

(Analysis Center of Agrobiology and Environmental Sciences of Zhejiang University, Hangzhou 310058, China)

Abstract: Bentonite contains a large amount of turbostratically disordered two-dimensional layered silicate minerals, such as montmorillonite, whose X-ray diffraction pattern only has 00l and hk (hk0) diffraction peaks. The normal Rietveld method is not possible to fit and separate these two kinds of diffraction peaks. In this paper, the Ufer-single layer supercell plane defect model was applied to the hk profile model of three-dimensional Rietveld method to fit and separate various diffraction peaks on the XRD spectra of various components of bentonite in order to calculate contents of its various components and to verify the accuracy of this method by analyzing validation and natural bentonite samples. The results show that the Ufer-single layer supercell modified Rietveld method can be used to have precisely fitted and separated various spectra on the XRD pattern and to have calculated accurate contents of various components of bentonite. Finally, the uncertainty of quantitative analytical results using this method has been analyzed and evaluated. The expanded uncertainties of montmorillonite, α-quartz, cristobalite are 0.6%, 0.6%, and 0.5%, respectively, at the 95% confidence level．

Keywords: bentonite; Rietveld refinement; quantitative phase analysis; Ufer-method; turbostratically disordered; uncertainty

ACTA MINERALOGICA SINICA Vol.43, No. 3, 2023, Page 416