Not long after Max von Laue's discovery of the diffraction of X-rays by single crystals, the first powder patterns were obtained by Friedrich from waxes and by Keene from thin metal sheets (1913). This led rapidly to the development of the Debye-Scherrer camera (1916) which uses a strip of photographic film to record the powder pattern. Debye-Scherrer cameras have limited resolution and so parafocusing cameras were developed. Seeman and Bohlin (1919) developed one of the earliest models. A more popular one developed by Guinier (1937) and subsequently modified by De Wolff (1948) is known as the Guinier-de Wolff camera. Other modifications were developed, e.g. for variable temperature work. Thus in 1969 the Guinier-Hägg camera was designed followed by the Guinier-Simon camera (1971). All of these use X-ray film to record the powder pattern.
Traditional powder X-ray diffractometry, in which the powder pattern is collected on a point by point basis with an X-ray photon detector, has developed more slowly. This can be attributed to the lack of sensitivity of the early detectors and the relative weakness of the powder lines compared to the "spots" from single-crystal studies. Although Geiger-Müller tubes were developed in 1928, and a non-focussing diffractometer was used by Le Galley in 1935, the most important development of the modern powder diffractometer is largely due to Parrish during and after World War II (1945).
By the late 1970's modern powder diffractometers were starting to replace camera methods for research, although the latter may still occasionally be found today in universities, where they are used for teaching purposes! In the last decade, a major step has been to introduce multidetectors in the X-ray laboratory so kinetic studies and thermodiffractometry can be performed within the confines of the laboratory.
|© Copyright 1997-2006. Birkbeck College, University of London.||Author(s): Jeremy Karl Cockcroft|