Ferroelastic structure AlNb_1/2Ta_1/2O₄ ceramics with improved thermophysical and mechanical properties

Effect 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 MPam(0.5). The brittleness index of AlNb1/2Ta1/2O4 (2.6 mu m(-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).