High temperature phase stability, sintering resistance and thermal conductivity of La2O3 and Y2O3 doped ZrO2 composites

La2O3-Y2O3-ZrO2(YSZ) composite ceramic powders with various La2O3 doping contents were prepared by chemical co-precipitation calcination method. High temperature phase stability, sintering resistance and thermo-physical properties of this composite ceramic powder were studied and also compared with those of the traditional YSZ ceramic powder in order to explore the possibility of La2O3-YSZ for thermal barrier coating material application. The crystal structure and phase composition of the ceramic powders were analyzed by XRD. The effect of La2O3 doping content on the high temperature phase stability of YSZ was investigated. SEM was used to analyze the microstructure of the sintered ceramics to investigate the effect of La2O3 doping on the sintering resistance of YSZ. Thermal diffusivity was tested by laser flash method and the thermal conductivity of material was obtained by calculation. The results indicate that YSZ and various La2O3 doping La2O3-YSZ are all composed of single non-equilibrium tetragonal phase ZrO2 (t'-ZrO2). After 100 h heat treatment at 1400 ℃, the t'-ZrO2 in YSZ has completely transformed to cubic phase ZrO2 (c-ZrO2) and monoclinic phase ZrO2 (m-ZrO2). In the 0.4mol%-1.4mol% La2O3 doping range, La2O3-YSZ exhibits good phase stability than that of YSZ. YSZ doped by 1.0mol% La2O3 (1.0mol% La2O3-YSZ) does not generate m-ZrO2 after thermal treatment, showing good high temperature phase stability. In addition, 1.0mol% La2O3-YSZ has better sintering resistance and lower thermal conductivity in comparison with YSZ. In the temperature range from room temperature to 700 ℃, the thermal conductivity of 1.0mol% La2O3-YSZ is 1.90-2.17 W/(m·K) which is obviously lower than that of YSZ (2.13-2.33 W/(m·K)). ©, 2015, Beijing University of Aeronautics and Astronautics (BUAA). All right reserved.