Measuring Techniques of Parallel Beam-Diffraction Micrography

Abstract

AbstractExamination of the substructure of crystalline solids by diffractographic methods has recently developed into an independent field of work alongside atomicstructure analysis. Diffraction micrography with electrons is characterized by the small size of the distortion fields and the high resolving power in small crystal ranges (1000-3000Å thickness). X-ray diffraction micrography is characterized by great reciprocation between wave field and distortion field and by undisturbed preparation and undisturbed testing in the large crystal ranges (up to 15 cm2). There are two groups of examination methods for diffraction micrography with X-rays: (1) Examination with a finely limited, polychromatic or monochromatic X-ray source and moving sample, according to A. R. Lang et al. (2) Examination with a parallel-ray beam of polychromatic or monochromatic X-rays with fixed sample, in accordance with Berg-Barrett et al. For the examination of coarse defects in single-crystalline and poly crystalline matter, the parallel-beam method offers a wide scope for studies in the physics and applications of single-crystal line and polycrystalline solids. This paper therefore includes a summary of the methods using collimation systems and grating diaphragms. Measuring techniques and results are illustrated with the help of reflection and transmission pictures on various crystals. The various methods and refined measuring technique of the parallel-beam method enable the following to be defined: (1) Localization of crystallites from 20 μ diam. upward in a surface up to 15 cm2. (2) Determination of the faces of averted crystallites from 20 µ diam. upward in crystal surfaces. (3) Angle of avertence of crystallites or curvature angles of net faces from 1 to 3° in crystal surfaces up to 15 cm2. (4) Subangle grain boundaries, slip bands, and dislocation lines; also distortion fields (from 20 μ upward) resulting from mechanical, thermal, and radiation damage.