Spinels can be disordered over cationic sites by having some of the B 3+ cations in tetrahedral rather that octahedral sites. The degree of inversion of a spinel describes the extent to which A 2+ and B 3+ cations occupy octahedral and tetrahedral sites respectively with the two extremities shown in Figure . A fully normal structure has all occupied tetrahedral sites consisting of A 2+ cations and all occupied octahedral sites consisting of B 3+ cations. A fully inverse spinel structure has one-half of occupied octahedral sites filled with A 2+ cations while the other half is filled with B 3+ cations and all occupied tetrahedral sites are filled with B 3+ . It is of note that due to the two different species across the octahedral sites in the inverse spinel structure, that there are many possible cation configurations for a fully inverse spinel whereas there is only a single normal configuration. The inversion in spinels results in a very large number of possible configurations.