Synthesis and thermophysical properties of (AlxY1-x)TaO4 ceramics as thermal barrier coating materials

YTaO4 is considered a promising thermal barrier material, and Al2O3-doped YTaO4 can significantly enhance the thermophysical properties of this material. In this paper, in order to study in detail the thermophysical properties of Al2O3 doped YTaO4, bulk (AlxY1-x)TaO4 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) ceramics were firstly prepared by hot-pressure sintering, the phase composition, microstructure and the thermal physical characteristics of the specimens were tested. The result shows that, the thermal conductivity of (AlxY1-x)TaO4 ceramics is substantially diminished due to the phonon-point defect scattering mechanism, with a minimal value of about 1.73 W m−1 K−1 at 1000 °C, which is about 31% lower than that of YSZ. The ultimate thermal conductivity of the (AlxY1-x)TaO4 ceramics is predicted by different theoretical models, and it is discovered that the thermal conductivity of the materials could be further reduced by Al2O3 doping. Moreover, the thermal expansion coefficient of (AlxY1-x)TaO4 ceramics (9.8–11.1×10−6 K−1, 1200 °C) is remarkably similar to that of YSZ. The superior thermophysical properties of (AlxY1-x)TaO4 ceramics make them a promising candidate for thermal barrier coatings.