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

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 degrees C. 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.