La_2O_3和Y_2O_3掺杂ZrO_2复合材料的高温相稳定性、抗烧结性及热导率

采用化学共沉淀煅烧法制备不同La2O3掺杂量的La2O3-Y2O3-ZrO2(YSZ)复合陶瓷粉末,研究该复合陶瓷粉末的高温相稳定性、抗烧结性及热物理性能,并与传统应用的YSZ陶瓷粉末进行对比,以探讨La2O3-YSZ作为热障涂层材料应用的可能性。采用XRD分析陶瓷粉末的晶体结构和物相组成,研究La2O3掺杂量对YSZ高温相稳定性的影响。采用SEM观察陶瓷烧结体的微观形貌,研究La2O3掺杂对YSZ抗烧结性的影响。采用激光脉冲法测定热扩散率,通过计算得到材料的热导率。结果表明:YSZ和不同La2O3掺杂量的La2O3-YSZ均由单一的非平衡四方相ZrO2(t′-ZrO2)组成。经1 400℃热处理100h后,YSZ中t′-ZrO2完全转变为立方相ZrO2(c-ZrO2)和单斜相ZrO2(m-ZrO2),在0.4mol%~1.4mol%La2O3掺杂范围内,La2O3-YSZ的相稳定性均优于YSZ,其中1.0mol%La2O3掺杂的YSZ(1.0mol%La2O3-YSZ)经热处理后无m-ZrO2生成,表现出良好的高温相稳定性。此外,1.0mol%La2O3-YSZ较YSZ具有较高的抗烧结性和较低的热导率。在室温至700℃范围内,1.0mol%La2O3-YSZ的热导率为1.90~2.17 W/(m·K),明显低于YSZ的热导率(2.13~2.33 W/(m·K))。

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 1 400 ℃, 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)).