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. RETa 3 O 9 compounds have a defect-perovskite structure, indicating that they have low thermal conductivity, which is the critical property of TBCs. Herein, dense RETa 3 O 9 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 RETa 3 O 9 were studied systematically, including specific heat, thermal diffusivity, thermal conductivity, thermal expansion coefficients, and high-temperature phase stability. The thermal conductivities of RETa 3 O 9 are very low (1.33-2.37 W/m·K, 373-1073 K), which are much lower than YSZ and La 2 Zr 2 O 7 ; and the thermal expansion coefficients range from 4.0 × 10 −6 K −1 to 10.2×10 −6 K −1 (1273 K), which is close to La 2 Zr 2 O 7 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, RETa 3 O 9 ceramics were promising candidate materials for TBCs.
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