- Mixed metal oxides.
- Cubic close packed system, cubic sites occupied by oxide
ligand, which are weak field ligands.
- Contain tetrahedral and octahedral holes Based on type of
metal atom occupying them, they are classified into two
- i. Normal Spinels
- Ii. Inverse Spinels or antispinels
» A+n represents a metal atom of charge +n
occupying a tetrahedral site.
» B+m represents a metal atom of charge +m
occupying an octahedral site.
» Bivalent ions occupy tetrahedral sites, trivalent
ions occupy octahedral sites.
» General Formula :
+3 O4 OR (AII)tet(BIII)2
» E.g Mn3O4 (i.e Mn+2Mn2
» MgAl2O4 (known as spinel), ZnFe2O4,
FeCr2O4 (chromite) etc.
» All bivalent cations and half the trivalent cations
in octahedral holes. The other half of trivalent
cations are in tetrahedral holes.
» General Formula B+2B+3A+3O4 or
» Since Oxide ions are weak field ligands, the
cations are found in high spin configurations.
» Finding out whether a given spinel is normal or
inverse, can be done by calculating CFSE for
» Greater the CFSE, more stable the structure and
hence the spinel takes that structure.
» Value of 10Dq for a trivalent cation is 1.5 times
more than that of a bivalent ion of the same
» Value of 10Dq is reduced by a factor of 4/9 on
going from an octahedral (B) site to a