Residual Stress and Strain:

• Strain in the crystal lattice will produce a distortion of the diffraction line. A typical case of uniform and non-uniform strain in the crystal lattice is shown in Figure 5.01 [1].

• Macrostrain causes the lattice parameters to change resulting in a peak shift. Glycolation or heating of clay minerals are examples of induced macrostrains .

• Tensile and compressive forces can produce microstrains resulting in a broadening of the diffraction peaks or peak asymmetry in some cases.

• Dislocations, vacancies, shear planes, etc., can produce microstress, which results in a distribution of peaks around the unstressed peak location, appearing like a crude broadening of the peak.

Williamson-Hall Plot (WHP) Method:

Considering both size and strain effect, Williamson and Hall developed a method to analyze the XRD peak as given below.

Ref.[1]: R. Jenkins, R. Snyde, Introduction to X-Ray Powder Diffractometry, John Wiley & Sons, Inc., Canada (1996)