Voigt-function model in diffraction linebroadening analysis, defects and microstructure: Analysis by diffraction (eds) R L Snyder et al (New York: Oxford University Press) p

Diffraction-line broadening routes are briefly reviewed. Both laboratory and synchrotron x-ray measurements of W and MgO showed that a Voigt function satisfactorily fits the physically broadened line profiles. The consequences of an assumed Voigt-function profile shape for both size-broadened and strain-broadened profiles (“double-Voigt ” method) are studied. It is shown that the relationship between parameters obtained by the Warren-Averbach approximation and integral-breadth methods becomes possible. Line-broadening analysis of W and MgO is performed by using the Warren-Averbach and "double-Voigt " approaches and results are compared. To appear in Microstructure Analysis from Diffraction, edited by R. L. Snyder, H. J. Bunge, and J. Fiala, International Union of Crystallography, 1999. 2List of symbols a, b, c, m, mN, U, V, W General constants z General variable A Fourier coefficient a Edge of orthorhombic cell, orthogonal to diffracting planes3 D "Apparent " domain size orthogonal to diffracting planes d Interplanar spacing e "Maximum " (upper limit) strain FWHM Full width at half maximum of profile f, F Pure-specimen (physically) broadened profile and its Fourier transform g, G Instrumentally broadened profile and its Fourier transform h, H Observed broadened profile and its Fourier transform hkl Miller indices I Intensity K Scherrer constant k $ /(B $), characteristic integral-breadth ratio of a Voigt functionC G1/2 L, L ’ na, column length (distance between two cells in a real space) orthogonal to 3 diffracting planes l Order of reflection MSS Mean-square strain n Harmonic number 3p Column-length distribution functio