Oxides of the 3<i>d</i>Transition Metals*

Abstract

The magnetic, electrical and optical properties of the 3d metal oxides are examined for clues to the energy band structure. A tentative energy band scheme is proposed for the oxides of scandium, titanium and vanadium which suggests that the nonbonding 3d orbitals of neighboring cations overlap sufficiently to form a 3d conduction band. The 3d orbitals do not overlap in the oxides of the remaining 3d metals, with the consequence that the 3d electrons are in isolated energy states and electron transport occurs by electron exchange between cation neighbors and involves an activation energy. An energy level scheme for these latter oxides is calculated from simple electrostatics, and it is shown to agree with the observed electrical properties. Conduction in these oxides includes transport of high-mobility holes in the 2p band of the oxygen lattice and of low-mobility holes and electrons in the 3d levels of the cation lattice.