An investigation into the surface phase of nanostructured zirconia by conventional UV spectroscopy

The phase features of nanostructured zirconia samples were characterized by conventional UV spectroscopy and XRD. While XRD identification shows the phase in the bulk of zirconia prepared by refluxing a ZrOCl2 solution and calcining at 673 K is pure monoclinic, a good few tetragonal ZrO2 in its surface regions was detected by surface-sensitive UV spectroscopy. Although about 50% of the zirconia from 353 K aging and calcining at 673 K exists as monoclinic in bulk, the surface structure is pure tetragonal. Results show that the thermodynamically feasible tetragonal phase always stays on the surface and the phase transition from tetragonal to monoclinic takes place initially at the core.