The thermo-mechanical properties and ferroelastic phase transition of RENbO4 (RE = Y, La, Nd, Sm, Gd, Dy, Yb) ceramics

In this work, RENbO 4 (RE = Y, La, Nd, Sm, Gd, Dy, Yb) ceramics with low density, low Young's modulus, low thermal conductivity, and high thermal expansion have been systematically investigated, the excellent thermo-mechanical properties indicate that RENbO 4 ceramics possess the potential as the new generation of thermal barrier coatings (TBCs) materials. X-ray diffraction and Raman spectroscopy phase structure identification reveal that all dense bulk specimens obtained by high-temperature solid-state reaction belonged to the monoclinic (m) phase with C12/c1 space group. The ferroelastic domains are detected in the specimens, revealing the ferroelastic transformation between tetragonal (t) and monoclinic (m) phases of RENbO 4 ceramics. The Young's modulus and hardness of the RENbO 4 ceramics measured by the NanoBlitz 3D nanoindentation method are discussed in details, and the lower Young's modulus (60-170 GPa) and higher hardness (the maximum value reaches 11.48 GPa) indicating that higher resistance of RENbO 4 ceramics to failure and damage. Lower thermal conductivity (1.42-2.21 W [m k] −1 at 500°C-900°C) and lower density (5.330-7.400 g/cm 3 ) than other typical TBCs materials give RENbO 4 ceramics the unique advantage of being new TBCs materials. Meanwhile, the thermal expansion coefficients of RENbO 4 ceramics reach 9.8-11.6 × 10 −6 k −1 and are comparable or higher than other typical TBCs materials. According to the first-order derivative of the thermal expansion rate, the temperature of the ferroelastic transformation of RENbO 4 ceramics can be observed.