Thermal expansion performance and intrinsic lattice thermal conductivity of ferroelastic RETaO ₄ ceramics

Ferroelastic RETaO 4 ceramics are promising thermal barrier coatings (TBCs) because of their attractive thermomechanical properties. The influence of crystal structure distortion degree on thermomechanical properties of RETaO 4 is estimated in this work. The relationship between Young's modulus and TECs is determined. The highest TECs (10.7 × 10 −6 K −1 , 1200°C) of RETaO 4 are detected in ErTaO 4 ceramics and are ascribed to its small Young's modulus and low Debye temperature. The intrinsic lattice thermal conductivity (3.94‐1.26 W m −1 K −1 , 100‐900°C) of RETaO 4 deceases with increasing of temperature due to an elimination in thermal radiation effects. The theoretical minimum thermal conductivity (1.00 W m −1 K −1 ) of RETaO 4 indicates that the experimental value is able to be reduced further. We have delved deeply into the thermomechanical properties of ferroelastic RETaO 4 ceramics and have emphasized their high‐temperature applications as TBCs.