Phase transformation in the surface region of zirconia detected by UV Raman spectroscopy

The phase transformation of zirconia from tetragonal to monoclinic is chara cterized by UV Raman spectroscopy, visible Raman spectroscopy, and XRD. Ele ctronic absorption Of ZrO2 in the UV region makes UV Raman spectroscopy mor e sensitive at the surface region than XRD or visible Raman spectroscopy. Z irconia changes from the tetragonal phase to the monoclinic phase with calc ination temperatures elevated and monoclinic phase is always detected first by UV Raman spectroscopy for the samples calcined at lower temperatures th an that by XRD and visible Raman spectroscopy. When the phase of zirconia c hanges from tetragonal to monoclinic, the slight changes of the phase at ve ry beginning can be detected by UV Raman spectroscopy. UV Raman spectra cle arly indicate that the phase transition takes place initially at the surfac e regions. It is found that the phase change from tetragonal to monoclinic is significantly retarded when amorphous Zr(OH)(4) was agglomerated to bigg er particles and the particle agglomeration of amorphous zirconium hydroxid e is beneficial to the stabilization of t-ZrO2 phase.