Cation distribution in the CuxMn3-xO4 and CuMxMn2-xO4 (M = Cr, Al) spinels

The Rietveld profile analysis method applied to x-ray diffraction data was used to assess the cation distribution in the CuxMn3 - xO4 (x = 0.5, 0.75, 1.00) solid solutions at 900 degreesC in air and after quenching and also in quenched CuCrxMn2 - xO4 and CuAlxMn2 - xO4 (0 less than or equal to x less than or equal to 2.0) solid solutions. The results show that the tetragonal distortion (c/a greater than or less than 1) of the spinel structure depends on the relative occupancies of the Jahn-Teller ions Cu2+ and Mn3+ on the octahedral and tetrahedral sites and also on whether the system is in an equilibrium or metastable state. The structure of the solid solutions may also be affected by clusterization of octahedral Jahn-Teller ions. The resultant contents of Jahn-Teller ions leading to one or the other type of tetragonal distortion are evaluated.