Advanced rare earth tantalate RETaO4 (RE=Dy, Gd and Sm) with excellent oxygen/thermal barrier performance

Thermal barrier coatings (TBCs) materials with lowered thermal and oxygen ion conductivity can provide thermal and oxidative protection for high temperature hot-end components in aeronautical engines and gas turbines . The rare-earth tantalate RETaO 4 (RE = Dy, Gd and Sm) ceramics with monoclinic (m) phase were successfully synthesized via spark plasma sintering . Oxygen vacancies responsible for the thermal and oxygen ion conductivities of RETaO 4 were demonstrated by atomic-resolution energy dispersive X-ray and X-ray photoelectron spectroscopy . Among the three samples, DyTaO 4 has excellent oxygen/thermal barrier performance. Compared to the current service thermal barrier coating material ZrO 2 -8 wt% Y 2 O 3 (8 YSZ), DyTaO 4 has an ultra-low oxygen ion conductivity benefiting from low oxygen vacancy concentration and strong stretching force constants. The intrinsic thermal conductivity of DyTaO 4 is 68.2% less than that of 8  YSZ . Additionally, the thermal expansion rate curves indicate that the phase transformation does not happen from room temperature to 1200 °C. The above results demonstrate that high-growth rate thermally grown oxide can be retarded by creating dense DyTaO 4 coating with lowered thermal and oxygen ion conductivity.