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

Abstract

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 (1.33‐2.37 W/m·K, 373‐1073 K), which are much lower than YSZ and La2Zr2O7; 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 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.

Theoretical and experimental investigations of mechanical properties for polymorphous YTaO4ceramics

“…Being analogous to ABO 3 perovskite structure, the YTa 3 O 9 compound possesses an orthorhombic (space group: Cmmm ) structure, which has two‐thirds vacancy in the sub‐lattice of RE site . Chen et al, had investigated the thermo‐physical properties of RETa 3 O 9 ceramics as potential thermal barrier coatings . The results reveal that the heat transfer of RETa 3 O 9 ceramics deviate from Umklapp scattering process, and the thermal conductivity increases with temperature increasing, which is pertinent to vacancy of RE sites.…”

Potential thermal barrier coating materials: RE3NbO7 (RE=La, Nd, Sm, Eu, Gd, Dy) ceramics

“…Figure depicts that the grain size of RE 3 NbO 7 is 1‐20 μm, which is several order of the phonon mean free path (nm). Furthermore, the influence of grain boundary scattering on phonon decreases dramatically with the increasing temperature and it can be omitted at elevated temperature . Hence, the extremely low thermal conductivity of RE 3 NbO 7 originates from the strong intrinsic crystal structure and lattice imperfection scattering.…”

Thermophysical properties of SmTaO4, Sm3TaO7 and SmTa3O9 ceramics

“…Sm 2 Zr 2 O 7 ceramics are applied in gas turbines with operating temperatures exceeding 1500°C owing to a unique property of samarium [26]. Chen et al investigated the thermophysical properties of RETa 3 O 9 ceramics as potential thermal barrier coatings [27]. The results reveal that the heat transfer of RETa 3 O 9 ceramics deviates from that of the Umklapp scattering process, and the thermal conductivity increases with increasing temperature, which is appropriate due to the vacancy of RE sites.…”