Preparation and Phase Stability of La_2O_3,Y_2O_3 Co-doped ZrO_2 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,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℃ 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℃ for 100h,LaYSZ still keeps single tetragonal ZrO2 structure,while 12mol% tetragonal phase of 8YSZ transforms to monoclinic phase.After heat-treatment at 1400℃ for 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.