Phase evolutions and structures of zirconium oxides with 2 percent yttrium before and after carbonization have been systemically studied with X-ray diffraction and Rietveld structural refinement. The carbonization decreases the structural stability of original ZrO2. According to the X-ray diffraction patterns, three phases with monoclinic, tetragonal and cubic structure coexist after carbonization. With increasing carbonizing temperature, the content of tetragonal phase in ZrO2with 2% mol Y2O3 doped increases，however, the phase content of monoclinic phase decreases. The content of tetragonal phase in ZrO2with 3% mol Y2O3doped increases greatly after carbonization. It implies that carbonization is beneficial for the formation of ZrO2tetragonal phase.
