LaAlO3作为热障涂层顶级涂层材料的评价

摘要

钙钛矿是一种多用途氧化物材料,可以通过调整成分而改变其性能以满足特定的需求.采用柠檬酸法制备LaAlO3,用XRD和FT-IR检测确认其钙钛矿结构,并评估其用于热障涂层(TBC)技术所需的性能.检测溶液前驱物的粘度并通过激光粒度仪分析其粒度.采用传统烧结和放电等离子烧结使材料致密化.用阿基米德法测试材料的表观孔隙率,并测试材料的导热系数和热膨胀系数.测试材料的高温(最高达1300℃)力学性能和断裂性能.结果表明,在1200～1400℃ 烧结的样品,其热膨胀系数为(5.5～6.5)×10?6 K?1,热导率为2.2～3.4 W/(m·K).在1000～1300℃ 范围内测量弹性模量和极限应力,通过微压痕测算的断裂韧性约为3 MPa/m1/2.热处理温度从1200℃ 提高到1500℃,材料发生明显致密化,密度从3.21 g/cm3提高到5.81 g/cm3,表明材料热处理的最低温度应为1400℃.在相变温度下,LaAlO3从菱方结构(R3c)转变为理想的立方结构(Pm3m),而其晶格尺寸的变化可以忽略.本研究报道的数据可用于比较涉及LaAlO3的不同TBC的力学和断裂行为,也可用于数值模拟.%Perovskite is a versatile group of oxide materials allowing their properties to be tailored by composition towards specific requirements. LaAlO3 was prepared to study and report its properties in the context of its potential in thermal barrier coatings (TBCs) technology. A citric acid method was used for synthesis and the perovskite structure was confirmed using XRD and FT-IR. Viscosity of the solution precursor was checked as well as the particle size by laser particle size analysis. Densification behavior of the material was followed by conventional sintering and by spark plasma sintering. Apparent porosity by the Archimedes method, thermal conductivity and thermal expansion coefficient were studied. Mechanical and fracture properties were measured at elevated temperatures up to 1300 ℃. For samples sintered at 1200?1400 ℃, coefficient of thermal expansion ranged from 5.5×10?6 to 6.5×10?6 K?1 and thermal conductivity ranged between 2.2 and 3.4 W/(m?K). Elastic modulus and ultimate stress were measured at 1000?1300 ℃, while by micro-indentation, fracture toughness was found to be 3 MPa·m1/2. As the sintering temperature increased from 1200 to 1500 ℃, significant densification from 3.21 to 5.81 g/cm3 was found, indicating that material annealing should be made at least at 1400 ℃. Under this condition, negligible dimensional change in phase transition temperature of LaAlO3 from the rhombohedral (R3c) to the ideal cubic (Pm3m) is found. Data reported in this work can be useful for comparing the mechanical and fracture behaviours of different TBCs developed involving LaAlO3 as well as input for numerical simulations.