Ferroelastic structure AlNb1/2Ta1/2O4 ceramics with improved thermophysical and mechanical properties

Abstract

AbstractEffect of B site doping on structural, thermophysical, and mechanical properties of AlNbxTa1‐xO4 ceramics obtained by solid‐phase sintering were investigated in this work. Ferroelastic domain structures derived from the reversible second‐order ferroelastic transformation between the tetragonal (t) and monoclinic (m) contribute to improving the high‐temperature fracture toughness of AlNbxTa1‐xO4 ceramics, and the room fracture toughness of AlNb1/2Ta1/2O4 ceramics is 3.4 MPa·m0.5. The brittleness index of AlNb1/2Ta1/2O4 (2.6 μm−0.5) is also lower than AlTaO4, which indicates that has better damage tolerance. Compared with single‐component AlTaO4 and AlNbO4, the AlNb1/2Ta1/2O4 has a lower thermal conductivity due to enhanced phonon scattering caused by mass disorder and lattice distortion effects. Additionally, AlNb1/2Ta1/2O4 has a good match with the coefficient of thermal expansion of ceramic matrix composites (CMCs), and hence, AlNb1/2Ta1/2O4 has a considerable potential to be the candidate material for thermal/environmental barrier coatings (T/EBCs).