ε-Scanning ― a method of evaluating the dimensional and orientational distribution of crystallites by X-ray powder diffractometer

When a specimen is rocked about the θ axis of an X-ray powder diffractometer with the detector fixed at a given Bragg peak 2θ B , the resulting diffraction pattern reflects both the dimensional and the orientational distribution features of the crystallites in the specimen. For instance, reproducible fluctuations in the pattern can be attributed to coarse crystallites in the specimen, and the magnitude of the fluctuations corresponds to that of the peak intensity obtained by the θ-2θ scanning method, whereas a systematic deviation of the averaged pattern from that estimated from the absorption factor gives the angular dependence of the preferred orientation of the specimen directly. This method of evaluating the specimen using the X-ray powder diffractometer is reliable and convenient because of its applicability under the same experimental conditions as in the usual θ-2θ scanning method.