Mechanical properties, thermal expansion performance and intrinsic lattice thermal conductivity of AlMO4 (M=Ta, Nb) ceramics for high-temperature applications

Abstract

The vital thermo-mechanical properties of thermal and environment barrier coatings (TBCs/EBCs) include high hardness, low Young's modulus, matching thermal expansion coefficients (TECs) with substrate and low thermal conductivity. The effect of distortion degree of crystal structure on thermo-mechanical properties of AlMO4 (M=Ta, Nb) ceramics are assessed in this work. AlMO4 ceramics display modest TECs and no phase transformation is detected from room temperature to 1200 ℃. The experiment thermal conductivity can be dropped further as the theoretical minimum thermal conductivity of AlTaO4 and AlNbO4 is 1.48 W m−1 K−1 and 1.05 W m−1 K−1, respectively. The temperature dependent phonon thermal diffusivity of AlMO4 ceramics has been confirmed; the intrinsic lattice thermal conductivity is determined. The extraordinary thermo-mechanical properties make it clear that AlMO4 ceramics are suitable for high-temperature applications.