Preparation and Phase Stability of La2O3, Y2O3 Co-doped ZrO2 Ceramic Powder Application for Thermal Barrier Coating

La2O3-Y2O3-ZrO2 (LaYSZ) green composite ceramic powder was prepared by converse chemical coprecipitation method. The powder was conglomerated and heata2treated to be suitable for plasma spraying. The chemical compositions, microstructures, flowability and apparent density, phase stability at high temperatures were analyzed by means of inductively coupled plasma-atomic emission spectrometre (ICP-AES), scanning electron microscope (SEM), hall flowmeter, X-ray diffraction, respectively. The results show that the green composite powder presents tetragonal ZrO2 phase structure at room temperature. After heat-treated at 1150 or 2h, the conglomerated powder with spherical shape and dense surface exhibits good flowability, which can be used for plasma spraying. After heat-treated at 1300 or 100h, LaYSZ still keeps single tetragonal ZrO2 structure, while 12mol% tetragonal phase of 8YSZ transforms to monoclinic phase. After heat-treatment at 1400 or 100h, the amount of monoclinic phase in LaYSZ is of 2mol%, and that in the 8YSZ is of 47mol%. It shows that La2O3, Y2O3 co-doped ZrO2 exhibits better phase stability than single Y2O3-doped ZrO2.