Debye-Scherrer cylindrical powder

Debye-Scherrer Cylindrical Powder Camera The Plan View... 

X-ray powder diffraction studies are perfonned both with films and with counter diffractometers. The powder photograph was developed by P Debye and P Scherrer and, independently, by A W Hull. The Debye-Scherrer camera has a cylindrical specimen surrounded by a cylindrical film. In another commonly used powder... 

The film is in contact with the cylindrical brass frame of the camera and is held in position by springs 8. Sharp edges E terminate the exposed part of the film abruptly. Light is excluded by a brass cover which fits over the whole camera the X-rav beam is admitted through a hole covered with black paper. Further details of the construction and use of Debye- Scherrer powder cameras can be found in a paper by... 

Cylindrical samples, which are common in the Debye-Scherrer cameras Figure 3.2), are also used in powder diffractometry. Similar to flat transmission samples, small amounts of powder are required in the cylindrical specimen geometry. This form of the sample is least susceptible to the non-random distribution of particle orientations, i.e. to preferred orientation effects. 

Early powder diffraction experiments relied mostly on the Debye-Scherrer experiment to record a diffractogram. A broad film strip set into a cylindrical chamber produced the first known two-dimensional powder diffraction data. In contrast to modern methods the thin equatorial strip was the only part of interest and intensities merely optically and qualitatively analysed. This changed drastically with the use of electronic scintillation counters. Intensities were no longer a matter of quality but quantity. Inevitably the introduction of intensity correction functions long known to the single-crystal metier, i.e. Lorentz and polarization corrections (see Section 14.3), made their way into the field of powder diffraction. 

Figure 5 2. The Debye-Scherrer powder method. An X-ray R passes through a collimator and then meets a powder preparation P. The reflections caused by P lie on cones of reflection, which form crescents or arcs on a cylindrical film F.

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