Spinels, normal and inverse structure of spinels.
Spinels are mixed oxides having the general formula AB2O4 or we can break it as AOB2O3 where A is a di-positive metal cation and B is a tri-positive metal cation. in these mixed oxides, oxide ions form a fcc arrangement, as A stays in octahedral void and B remains in the tetrahedral void. This is called normal spinel structure. In contrast, if A goes to tetrahedral void and half of B goes to octa hedral void then that mixed oxide will be called as inverse spinel. That means half of B will be in octahedral void and other half of B will be in tetrahedal void. In a spinel both A and B can be same or different. for example : Mn3O4 and ZrCr2O4. How to determine whether the spinel will be normal or inverse spinel? It is all about stability of the ions in corresponding voids, that means if the di-positive ion A has more CFSE in octahedral field then it will stay in octahedral void as a result the spinel will be an inverse spinel and if B has more CFSE in octahedral fie...