12. Powder Diffraction

The powder method was devised by Hull soon after the discovery of X-ray diffraction, and developed in detail by Hull [1] and by Debye and Scherrer [2]. Since that time, X-ray diffraction from powdered specimens has been used in divers investigations of materials. The main interest in this book is structure determination for which powder methods have, until recent years, been inappropriate, mainly because of the problem of overlap of the X-ray reflections which causes three-dimensional data information to collapse on to a one-dimensional powder record. The vast improvement in instrument technology in recent years has led to powder photographs and diffractograms of sufficient precision to be interpretable in terms of the underlying crystal structures, and powder techniques have now been developed as a very significant tool in X-ray structure determination. Before launching into this topic, however, we summarize here some of the many applications of X-ray powder diffraction other than in crystal structure determination.