Quantitative analysis of multicomponent powders by full-profile refinement of Guinier–Hägg X-ray film data

Abstract

Full-profile analysis of microdensitometer-measured Guinier-H~igg X-ray powder film data (strictly monochromatized Cu K~I radiation) [see Malmros & Thomas (1977). J. Appl. Cryst. 10,[7][8][9][10][11] is here extended to treat a multicomponent system where two of the components are refinable. The method is demonstrated for the case of: (a) ~-Bi203/KC1 (standard), and (b) CaF2/SiO2 (s-quartz) together with a Mg(OH)2 matrix. In (a), a weight ratio BizO3/KCI of 1:1 gave an experimental result of 0-96(9):1. In (b), a number of admixtures have been studied in the range 1-60 wt% SiO2 all with 10 wt % CaF2. The agreement between weight ratios and profile refinement results suggests that the formal temperature factors function as effective absorption correction parameters. It is thus shown that approximate quantitative analysis is feasible from Guinier-H~igg diffraction data without any previously determined calibration curve. Moreover, the method permits the use of all available overlapping data in the refinement of a structure without needing to exclude data from known impurities [see Waltersson, Werner & Wilhelmi (1977). Cryst. Struct. Commun. 6,[231][232][233][234][235].This feature is likely to prove the most common application of the method.

Quantitative phase analysis from neutron powder diffraction data using the Rietveld method

“…The Rietveld method calculates the peak intensities directly from crystal structure parameters, and so it has the advantage of permitting the determination of phase abundance without precalibration of either the experimental or calculated kind (Werner et al, 1979;Weiss et al, 1983). Of course, the same advantage is present when integrated intensities are obtained by calculation but in this case the deconvolution of overlapping peaks in complex diffraction patterns remains a serious limitation of the method.…”

“…If step-scan diffraction data are collected, the determination of relative intensities need not be restricted to individual peaks, or even to groups of peaks, but can be extended to incorporate the entire diffraction pattern by the use of 'whole-pattern' fitting procedures (Werner, Salome, Malmros & Thomas, 1979;Weiss, Kraji6ek, Smr6ok & Fiala, 1983;Toraya, Yoshimura & Somiya, 1984;Smith, Johnson & Ruud, 1986). This technique has the advantages of (i) permitting partially overlapping (as well as free-standing) reflections to contribute to the analysis, and of (ii) 'averaging out' most of the effects of preferred orientation, extinction and other systematic aberrations.…”

The Rietveld method in neutron and X-ray powder diffraction

“…Impurities may be deliberately added to reduce preferred orientation. The simultaneous refinement of two or more phases is a feature which has been incorporated in a number of programs (Werner, Salome, Malmros & Thomas, 1979;Worlton, Jorgensen, Beyerlein & Decker, 1976).…”

Quantitative Phase Analysis using the Whole-Powder-Pattern Decomposition Method. I. Solution from Knowledge of Chemical Compositions

“…Methods in the other category are based on the whole-powder-pattern fitting, and are rather new approaches. One is the use of Rietveld refinement (Werner, Salome & Malmros, 1979;Toraya, Yoshimura & Somiya, 1984;Hill & Howard, 1987) and another utilizes digitized whole-pattern traces (Smith, Johnson, Scheible, Wims, Johnson & UUmann, 1987;Smith, Johnson, Kelton & Andersen, 1989).…”