An X-ray diffraction study of disorder in MgFe2O4 and Mg(Cr, Al)O4

The X-ray diffraction line profiles obtained from the spinels MgFe 2 O 4 and Mg(Cr, Al)O 4 have been examined by a step-scanning diffractometer and found to be broadened. An analysis of the variance of the profiles is carried out using the techniques developed by Langford and Wilson, and from this it is concluded that mistakes are the probable origin of broadening in both cases. Further analysis suggests that these mistakes are associated with variable composition. Evidence is presented in support of order in the arrangement of Cr 3+ ions in Mg(Cr, Al)O 4 while MgFe 2 O 4 appears to have a random mistake structure.