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Precision X-Ray Diffractometry using Powder Specimens*

  • L. F. Vassamillet (a1) and H. W. King (a2)

Abstract

The counter tube diffractometer method for determining d spacings is often rejected for precision work because of lack of information concerning the nature and significance of the inherent errors. Errors concerned with the geometry of the method, the nature of the X-ray source, and the technique of collecting data have all been analyzed previously in some detail. The findings of these analyses, which are scattered throughout the literature, are reviewed briefly. Errors arising from imperfections in the instrument and misalignment of the X-ray source with respect to the diffractometev have been studied experimentally. The results are presented and discussed in terms of the resultant error in the determination of the lattice parameter of a cubic crystal. Errors determined both analytically and empirically are discussed in relation to the extrapolation procedures commonly used for diffractometers. It is shown that, depending on the construction of the instrument, the effect of imperfections in the gears may almost double the error in the final extrapolated value of a lattice parameter.

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Former Fellow of the Mellon Institute, Pittsburgh 13, Pennsylvania.

*

This work was supported in part by the U.S. Atomic Energy Commission, Washington, D.C.

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References

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1. Wilson, A. J. C., “Geiger-Counter X-ray Spectrometer—Influence of Size and Absorption Coefficient of Specimen on Position and Shape of Powder Diffraction Maxima,” J. Sci. Instr. 27(12): 321, December, 1950.
2. Parrish, W., “Results of the I.U.Cr. Precision Lattice-Parameter Project,” Acta Cryst. 13(10): 838, October, 1960.
3. Lonsdale, K., International Tables for X-ray Crystallography, Vol. III, 1962, Kynach Press, Birmingham, England, Acta Cryst. 3: 400, 1950.
4. Wilson, A. J. C., “Some Problems in the Definition of Wavelengths in X-ray Crystallography,” Zeit. Krist. 3: 471, 1959.
5. Lang, A. R., “Effect of Dispersion and Geometrical Intensity Factors on X-ray Back-Reflection Line Profiles,”.J. Appl. Phys. 27: 485, 1956.
6. Pike, E. R., “Counter Dififractometei—The Effect of Dispersion, Lorentz and Polarization Factors on the Position of X-ray Powder Diffraction Lines in Terms of the Center of Gravity of the Lines,” Acta Cryst. 12: 87, 1959.
7. Wilson, A. J. C., “Effect of Absorption on Mean Wave-Length of X-ray Emission Lines,” Proc. Phys. Soc. (London) 72: 924, 1958.
8. Cermak, J., “The Intensity Distribution in the Faces of Curved Crystal Monochromators and an Estimate of Its Influence on Precision Measurements of Lattice Parameters,” Acta Cryst. 13: 832, 1960.
9. Wilson, A. J. C., “Correction of Lattice Spacings for Refraction,” Proc. Comp. Phil. Soc. 36: 485, 1940.
10. Pike, E. R., “Counter Diffractometer—The Effect of Vertical Divergence on the Displacement and Breadth of Powder Diffraction Lines,” J. Set. histr. 34: 355, September, 1957 and 36: 52, January, 1959.
11. Klug, H. P. and Alexander, L. E., X-ray Diffraction Procedures, first edition, John Wiiey & Sons, Inc., New York, 1954.
12. Parrish, W. and Wilson, A. J. C., International Tables-for X-ray Crystallography, Vol. 11: 216, 1959, Kynach Press, Birmingham, England.
13. Evans, J. C. and Taylerson, C. O., “Measurement of Angle in Engineering,” Nat. Phys. Lab. Notes on Appl. Sci. No. 26, 1961, H.M. Stationery Office, London.
14. King, H. W. and Vassamillet, L. F., “precision Lattice Parameter Determination by Double Scanning Diffractometry,” Advances in X-ray Analysis, Vol. 5, University of Denver, Plenum Press, New York, 1962, pp. 7885.
15. Furnas, T. C. Jr. and White, E. W., “New Instruments for X-ray Analysis,” Advances in X-Ray Analysis, Vol. 4, University of Denver, Plenum Press, New York, 1960, p. 521.
16. Bond, W. L., “Precision Lattice Constant Determination,” Acta Cryst. 13: 814, 1960.
17. Pike, E. R. and Wilson, A. J. C., “Counter Diffractometer—The Theory of the Use of Centroids of Diffraction Profiles for High Accuracy in the Measurement of Diffraction Angles,” Brit. J. Appl. Phys. 10: 57; 1959.
18. Ladell, J., Parrish, W., and Taylor, J., “Centcr-of-Gravity Method of precision Lattice Parameter Determination,” Acta Cryst. 12: 253, 1959 and “Interpretation of Diffractometer Line Profiles,” Acta Cryst. 12: 561, 1959.

Precision X-Ray Diffractometry using Powder Specimens*

  • L. F. Vassamillet (a1) and H. W. King (a2)

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