Synthesis and thermophysical properties of RETa3O9 (RE=Ce, Nd, Sm, Eu, Gd, Dy, Er) as promising thermal barrier coatings

Thermal barrier coatings (TBCs) are one of the most important materials in gas turbine to protect the high temperature components. RETa3O9 compounds have a defect-perovskite structure, indicating that they have low thermal conductivity, which is the critical property of TBCs. Herein, dense RETa3O9 bulk ceramics were fabricated via solid-state reaction. The crystal structure was characterized by X-ray diffraction (XRD) and Raman Spectroscope. Scanning electron microscope (SEM) was used to observe the microstructure. The thermophysical properties of RETa3O9 were studied systematically, including specific heat, thermal diffusivity, thermal conductivity, thermal expansion coefficients, and high-temperature phase stability. The thermal conductivities of RETa3O9 are very low (1.33-2.37W/m.K, 373-1073K), which are much lower than YSZ and La2Zr2O7; and the thermal expansion coefficients range from 4.0x10(-6)K(-1) to 10.2x10(-6)K(-1) (1273K), which is close to La2Zr2O7 and YSZ. According to the differential scanning calorimetry (DSC) curve there is not phase transition at the test temperature. Due to the high melting point and excellent high-temperature phase stability with these oxides, RETa3O9 ceramics were promising candidate materials for TBCs.