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Analysis of the Broadening of Powder Pattern Peaks using Variance, Integral Breadth, and Fourier Coefficients of the Line Profile

Published online by Cambridge University Press:  06 March 2019

N. C. Halder
Affiliation:
Yale University, New Haven, Connecticut
C. N. J. Wagner
Affiliation:
Yale University, New Haven, Connecticut
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Abstract

The broadening of powder pattern peaks has been studied by three methods—Fourier analysis, integral breadth measurements, and variance of the line profiles. The results obtained from the variances are compared with those obtained from the integral breadths and Fourier coefficients.

Tungsten filings were prepared at room temperature and their powder pattern peaks were recorded with a Norelco diffractometer using filtered Cu Kα radiation. The variances, integral breadths, and Fourier coefficients were calculated with the IBM 7094 computer. The results indicate that the variance is very sensitive to the range of integration s2s1 = (2θ2 − 2θ1) cos θ0/λ. An error of ± 10% in this range due to the difficulty in choosing the correct background changes the values of the variance significantly and the integral breadth to a lesser extent. However, the same error does not affect the values of the Fourier coefficients.

Comparing the particle sizes and strains obtained by the three methods, it was found that the strains agreed remarkably well. The particle size calculated from the variance was smaller (DeW = 150Å) than that evaluated from the initial slope of the Fourier coefficients (De – 210Å) and from the integral breadths 2DeD1 = 430Å.

Type
Research Article
Copyright
Copyright © International Centre for Diffraction Data 1965

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