Limits of accuracy in the determination of lattice parameters and stresses by the Debye-Scherrer method

. The chief factor in limiting the presently attained accuracy of lattice-parameter determinations and stress evaluations by X-rays is the spectral width of the primary characteristic radiation. At large angles, where the line is most sensitive to changes of lattice dimension, the spectral width predominates over the width due to the geometry of the usual collimating systems. The accuracy of parameter determinations is limited essentially by the accuracy with which the center of such a line can be measured. For a diffraction line with a smooth intensity distribution, recorded on film, the error of measurement caused by the irregular fluctuations of density arising from the film grain is determined experimentally. It is shown that the present accuracy of stress measurements by X-rays has, in favorable cases, reached the limit given by the spectral width of the characteristic radiation.