Powder cameras vary in quality and precision of manufacture. If the camera(s) that were used to prepare the films are available, they should be checked using a standard such as Si powder to ascertain if they are indeed of the proper diameter. A standard reference such as Klug and Alexander (H.P. Klug and L.E. Alexander. 1954. X-ray Diffraction Procedures. John Wiley & Sons, New York. 716 p.) should be consulted on methods of sample preparation and sources of error.



Film is subject to many variables during exposure and processing. Inclusion of a standard, such as Si powder, in the sample will provide an internal check of film shrinkage; however, in some cases it may not be possible to do this (for reasons of peak interference, etc.). One technique is to run a pure standard and check shrinkage using a controlled set of development and processing steps. As long as the film is subjected to the same conditions, shrinkage should be the same.



A standard Debye-Scherrer powder camera has limited resolution and cannot be pushed beyond certain limits. I have found that specimens mounted as a sphere mount with a diameter of only 0.1 mm can be used to obtain good diffraction patterns. Using these tiny mounts increases the resolution that can be obtained, but at a cost of exposure time and difficulty in preparing the sample for mounting. A rotated sphere mount essentially eliminates preferred orientation and is the main advantage of using this technique.


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