Surfaces UV Raman spectroscopy XRD Nd 2 O 3 Characterization methodsThe Nd 2 O 3 modified ZrO 2 was synthesized using two methods of co-precipitation (Nd-ZrO 2 ) and wet impregnation (Nd/ZrO 2 ). The surface and bulk crystalline phases of Nd 2 O 3 modified ZrO 2 were investigated by using UV Raman spectroscopy, visible Raman spectroscopy, and X-ray diffraction (XRD). It is observed that the tetragonal phase in the surface region of Nd-ZrO 2 was not effectively stabilized by Nd 2 O 3 , as Nd 2 O 3 is mainly present in the bulk of Nd-ZrO 2 . However, in Nd/ZrO 2 , it is found that with the impregnation of 0.5 mol% Nd 2 O 3 on ZrO 2 , the surface tetragonal phase of Nd/ZrO 2 can be stabilized even after calcination at 700 Β°C. The UV Raman results indicate that a disordered structure, or intermediate structure, which is involved in the transition from the tetragonal to the cubic phase, is formed at the surface region of Nd/ZrO 2 . The formation of the aforementioned intermediate structure inhibits the phase transition from tetragonal to monoclinic in the surface region of Nd/ZrO 2 . Furthermore, it is observed that the mixed tetragonal and monoclinic phases in the surface region of ZrO 2 which has been impregnated with Nd 2 O 3 can also be stabilized after calcination at 700 Β°C. This work provides a simple method for controlling the surface phase of ZrO 2 at high temperatures.