The study of surface properties of ZrO2

The surface properties of ZrO2 in He, H2, O2, air and wet air at temperatures ranging from 25 to 600 8C have been investigated by means of ESR method. The Zr3þ centers characterized by ESR can be described as the oxygen coordinatively unsaturated Zr sites, mainly located at the corner sites of ZrO2 microcrystallites, on the surface of ZrO2. More Zr3þ centers were formed on the surface of ZrO2 by treating the sample in He at temperatures above 400 8C. And the formation of the Zr3þ centers may be associated with the removal of surface hydroxyl. Although Zr4þ in ZrO2 cannot be reduced at temperatures of up to 600 8C in H2, some surface hydroxyl can be reduced to form F-centers at temperatures higher than 250 8C. And O2 can be produced from the Zr3þ centers and F-centers at temperatures above 400 8C, and it may be associated with both H2 and the trace amount of O2 in H2. # 2003 Published by Elsevier B.V.