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 st...
