Crystallite-Size Determination of MgO by X-Ray Diffraction Line Broadening

The Scherrer equation which relates the pure diffraction breadth to crystallite size of the diffracting substance is applied to a study of various heat-treated MgO powders. A statistical treatment is used to examine effects of sample preparation and the diffraction system and to determine the degree of accuracy of the method. The procedure as described should give a relative accuracy in the 10,000 A range of ± 10 percent, and measurements may be made to 100,000 A. Comparison of the X-ray data with electron micrographs indicated that the latter gave information with regard to aggregate, not crystallite size. Aggregates grow only slightly with increased temperature treatment. Within the aggregates, individual crystallites grow moderately to 600°C, then greatly increase in size with increased temperature to 1600°C. Low temperature treated MgO has a dilated unit cell which tightens to a constant value after treatment to about l000°C