Additive Element Effects on Electronic Conductivity of Zirconium Oxide Film.

A theoretical study on the electronic structure of zirconium oxide using a molecular orbital method was carried out to investigate the additive element effects on the electronic conductivity of oxide film formed on Zr-alloys. The atomic clusters used were (MZri12O8)36+(M=Zr, 3d-transition metals and alkali metals). To simulate the electron conduction process in the oxide, calculations for a cluster with oxygen vacancy (V0) were also carried out. The energy gap Eg between electron-occupied and empty levels was evaluated, and the electronic conductivity was estimated qualitatively. Opposite effects on the electronic conductivity were found for additions of 3d-transition metals and alkali metals. The latter increased the electronic conductivity by forming impurity levels with small EQ. The former, however, induced compressive strain in the oxide, resulting in a lowering of electronic conductivity due to widening of the energy gap at the oxygen vacancy.