Influence of Lu3+addition on the structure, mechanical and thermophysical properties of Gd3TaO7 oxide

To optimise the mechanical and thermophysical properties of Gd3TaO7, Lu3+ doped Gd3TaO7 oxides were synthesised using sol-gel and high-temperature sintering methods. The results show that nanopowders with uniform particle sizes and bulk samples with compact microstructures were successfully obtained. Owing to the decreased order degree of lattice with increasing fraction of Lu3+, the lattice of (Gd1_xLux)3TaO7 transforms gradually from an ordered pyrochlore (x <= 0.5) into a disordered fluorite (x >= 0.7). The Young's modulus (174-192 GPa), Vickers hardness (9.9-10.9 GPa), and fracture toughness (2.61-3.68 MPa m0.5) of the bulk samples are superior or comparable to those of Y2O3-stabilised zirconia (YSZ), which can prolong the service life of thermal barrier coating. The thermal conductivity of (Gd1_xLux)3TaO7 (0.976-1.628 W m_1 K_1, 50-1000 degrees C), first decreases and then elevates with increasing fraction of Lu3+. Owing to the intensive phonon scattering caused by high-concentration point defects, the thermal conductivity of (Gd1_xLux)3TaO7 is approximately half that of YSZ. Additionally, the excellent lattice steadiness up to 1400 degrees C and high average thermal expansion coefficient (>= 10.71 x 10_6 K_1, 1000-1400 degrees C) of (Gd1_xLux)3TaO7 oxides will assist in preventing the pre-mature failure of thermal barrier coating.