International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 8.6, p. 712

Section 8.6.2.4. Preferred orientation and texture

A. Albinatia and B. T. M. Willisb

aIstituto Chimica Farmaceutica, Università di Milano, Viale Abruzzi 42, Milano 20131, Italy, and bChemical Crystallography Laboratory, University of Oxford, 9 Parks Road, Oxford OX1 3PD, England

8.6.2.4. Preferred orientation and texture

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Preferred orientation is a formidable problem which can drastically affect the measured intensities. A simple correction formula for plate-like morphology was given by Rietveld (1969[link]). Ahtee, Nurmela, Suortti & Järvinen (1989[link]) have shown how the effects of preferred orientation can be included in the refinement by expanding the orientation distribution in spherical harmonics. Quantitative texture analysis based on spherical harmonics has been implemented in the Rietveld refinement code by Von Dreele (1997[link]). A general model of the texture has also been described by Popa (1992[link]). It may be possible to remove or reduce the effect of preferred orientation by mixing the sample with a suitable diluent.

An additional problem is caused by particle size and strain broadening, which are not smooth functions of the diffraction angle. These effects can be taken into account by phenomenological models (e.g. Dinnebier et al., 1999[link]; Pratapa, O'Connor & Hunter, 2002[link]) or by an analytical approach such as that of Popa & Balzar (2002[link]).

The determination of the elastic stresses and strains in polycrystals can be determined from diffraction line shifts using Rietveld refinement (Popa & Balzar, 2001[link]).

References

Ahtee, M., Nurmela, M., Suortti, P. & Järvinen, M. (1989). Correction for preferred orientation in Rietveld refinement. J. Appl. Cryst. 22, 261–268.
Dinnebier, R. E., Von Dreele, R. B., Stephens, P. W., Jelonek, S. & Sieber, J. (1999). Structure of sodium parahydroxybenzoate by powder diffraction: application of a phenomenological model of anisotropic peak width. J. Appl. Cryst. 32, 761–769.
Popa, N. C. (1992). Texture in Rietveld refinement. J. Appl Cryst. 25, 611–616.
Popa, N. C. & Balzar, D. (2001). Elastic strain and stress determination by Rietveld refinement: generalized treatment for textured polycrystals for all Laue classes. J. Appl. Cryst. 34, 187–195.
Popa, N. C. & Balzar, D. (2002). An analytical approximation for a size-broadened profile given by the lognormal and gamma distributions. J. Appl. Cryst. 35, 338–346.
Pratapa, S., O'Connor, B. & Hunter, B. (2002). A comparative study of single-line and Rietveld strain-size evaluation procedures using MgO ceramics. J. Appl. Cryst. 35, 155–162.
Rietveld, H. M. (1969). A profile refinement method for nuclear and magnetic structures. J. Appl. Cryst. 2, 65–71.
Von Dreele, R. B. (1997). Quantitative texture analysis by Rietveld refinement. J. Appl. Cryst. 30, 517–525.








































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