Abstract: Akind of ZrO₂ nanopowder annealed at different temperatures in H₂ has been studied by ESR. On the surface of ZrO₂, about 1×10^-7 mol/g of Zr³⁺ centers are detected, which are the oxygen coordinatively unsaturated Zr. When the annealing temperature is lower than 400℃, the amount of Zr³⁺ center remains almost unchanged, while the amount of F-center increases in this temperature range, which may be resulted from the reduction of surface hydroxyl by H₂. When the annealing temperature is higher than 400℃, O₂^- is originated on the surface of ZrO₂, which may be formed from the reaction of Zr³⁺ and F-center with the trace amount of O₂ in ordinary H₂, and simultaneously, some Zr³⁺ centers are created, as being accompanied with the removal of surface hydroxyl.

Key words: ZrO₂, O₂/H₂, Surface effect, Zr³⁺ center, F-center