METAL-INSULATOR-TRANSITION IN NEARLY STOICHIOMETRIC CAVO3

A metal-to-insulator (MI) transition in perovskite-type vanadium oxide CaVO(y) in the vicinity of oxygen stoichiometry is reported. In spite of good metallic conductivity for stoichiometric CaVO(y) (y = 3.00), very slight oxidation (y congruent-to 3.05) causes the system to be in sulating but does not induce any significant structural changes. This type of MI transition is contrary to that reported on another d1 syste m LaTiO(y), which is a Mott-Hubbard insulator for y = 3.00 but becomes metallic by oxidation. We suggest that in CaVO(y), extra oxygens prim arily induce additional scattering which causes the metallic CaVO3 to be insulating.