Thermophysical and thermochemical properties of new thermal barrier materials based on Dy2O3–Y2O3 co-doped zirconia

Dy2O3-Y2O3 co-doped ZrO2 would potentially give lower thermal conductivity and higher coefficient of thermal expansion, which is a promising ceramic thermal barrier coating material for aero gas turbines and high temperature applications in metallurgical and chemical industry. In this study, Dy2O3-Y2O3 co-doped ZrO2 ceramics were prepared using solid state reaction methods. Dy0.5Zr0.5O1.75 and Dy0.25Y0.25Zr0.5O1.75 consist of pure cubic fluorite phase, whereas both Dy0.06Y0.072Zr0.868O1.934 and Dy0.02Y0.075Zr0.905O1.953 have tetragonal and cubic composite phases. The influence of the chemical composition on coefficient of thermal expansion (CTE) and the thermal conductivity was investigated by varying the content of rare earth dopant. Dy0.06Y0.072Zr0.868O1.934 exhibited a lower thermal conductivity and higher coefficient of thermal expansion as compared with standard 8 wt.% Y2O3 stabilized ZrO2 which is used in conventional thermal barrier coatings. The compatibility between the thermally grown oxide that consists of Al2O3 and the new compositions is critical to ensure the durability of thermal barrier coatings. Hence, the compatibility between Al2O3 and Dy2O3-Y2O3 codoped YSZ was investigated by mixing two types of powders and eventually sintered at 1300˚C. Dy0.06Y0.072Zr0.868O1.934 is compatible with Al2O3, whereas YAlO3 and Dy3Al2(AlO4)3 were formed when Dy0.25Y0.25Zr0.5O1.75 and Al2O3 were mixed and sintered