Preparation and properties of La₂(Zr_0.7Ce_0.3)₂0₇ ceramic for thermal barrier coatings

The synthesis kinetics and phase structure of La₂(Zr_0.7Ce_0.3)₂0₇ (LZ7C3) ceramic was investigated. The preparation composition was designed according to the mass loss in the synthesis process. LZTC3 powder was prepared successfully by a solid state reaction method and its atom ratio of La:Zr:Ce is close to the theory value of 10:7:3. The phase composition, microstructure, and thermophysical properties of the powder were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), the laser-flash method and the pushing-rod method. XRD results reveal that LZ7C3 is a mixture of La₂Zr₂0₇ (LZ) with pyrochlore structure and La₂Ce₂0₇(LC) with fluorite structure, and its main phase is the LZ solid solution. The thermal conductivity of LZ7C3 decreases gradually with increasing temperature; at 1473 K its value is 0. 79 W·m^-1·K^-1, which is almost 50% lower than that of LZ. The thermal expansion coefficient is 20% larger than that of LZ, and its value is 11.6 x 10^-6 K^-1 at 1 473 K. These results show that LZ7C3 ceramic can be explored as a novel prospective candidate material for use in new thermal barrier coating systems in the future.