ADDITIVE ELEMENT EFFECTS ON ELECTRONIC CONDUCTIVITY OF ZIRCONIUM-OXIDE FILM

A theoretical study on the electronic structure of zirconium oxide usi ng a molecular orbital method was carried out to investigate the addit ive element effects on the electronic conductivity of oxide film forme d on Zr-alloys. The atomic clusters used were (MZr12O8)36+ (M = Zr, 3d -transition metals and alkali metals). To simulate the electron conduc tion process in the oxide, calculations for a cluster with oxygen vaca ncy (Vo) were also carried out. The energy gap E(g) between electron-o ccupied and empty levels was evaluated, and the electronic conductivit y was estimated qualitatively. Opposite effects on the electronic cond uctivity were found for additions of 3d-transition metals and alkali m etals. The latter increased the electronic conductivity by forming imp urity levels with small E(g). The former, however, induced compressive strain in the oxide, resulting in a lowering of electronic conductivi ty due to widening of the energy gap at the oxygen vacancy.