Microstructural evolution and thermal-physical properties of YTaO4 coating after high-temperature exposure

YTaO4 is a promising candidate materials for next thermal barrier coatings (TBCs) due to low thermal conductivity, high thermal expansion coefficients, high melting point and low modulus. However, the current research on YTaO4 coating is relatively limited, there are obvious gaps of thermo-mechanical properties between bulks and coating. In this work, the YTaO4 coating was deposited on graphite substrate and TC4 substrate via atmospheric plasma spraying (APS). The phase transition temperature of M <-> T phase is about 1426 +/- 7 degrees C, which cause to the formation of ferroelastic domain structure. YTaO4 coating have an excellence anti-sintering performance due to a stable porosity during heat treatment, and the bonding strengths of YTaO4 coating on TC4 substrate has the maximum (35.12 +/- 2.34 MPa) when the top coating thickness is similar to 250 mu m. Compared with YTaO4 bulk, the thermal conductivity (0.53 W center dot m(-1)center dot K-1, 900 degrees C) of YTaO4 coating is reduced by 67-70 % in the entire temperature range. The low thermal conductivity for YTaO4 coating is the results of phonon scattering by porosity, domain boundaries and point defects. Moreover, the healing of intersplat pores with the increase of sintering temperature had significantly improved the hardness and elastic modulus of the coating.