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 heat-treated to be suitable for plasma spraying. The chemical compositions I 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 degrees C for 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 degrees C for 100h, LaYSZ still keeps single tetragonal ZrO2 structure, while 12mol% tetragonal phase of 8YSZ transforms to monoclinic phase. After heat-treatment at 1400 degrees C for 100h, the amount of monoclinlic 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.