Mechanical, thermal and CMAS resistance properties of high-entropy (Gd0.2Y0.2Er0.2Tm0.2Yb0.2)2Zr2O7 ceramics

A high entropy zirconate ceramic (Gd0.2Y0.2Er0.2Tm0.2Yb0.2)2Zr2O7 (HEZ) with fluorite structure has been synthesized by solid state reaction and high temperature sintering successfully. The investigation indicated that HEZ has ultra-low thermal conductivity (0.82 W × m−1 × K−1 at 1200 °C), similar thermal expansion coefficient (10.61 × 10−6 K−1 at 1300–1400 °C) with that of YSZ, excellent mechanical properties (hardness, elastic modulus, fracture toughness), and great CMAS corrosion resistance. Emphasis is given to discussing the CMAS wetting, corrosion process and failure mechanisms using high-temperature in-site wetting method and transmission electron microscopy (TEM). The results show that the HEZ exhibits better corrosion resistance than single rare earth zirconate Gd2Zr2O7 due to the coupling effect of anti-wettability, gradient diffusion rate and multicomponent apatite crystallization produced by doping rare earth ion (Gd3+, Y3+) close to Ca2+ radius and rare earth ion (Er3+, Tm3+, Yb3+) with small ion radii. In the comprehensive view, (Gd0.2Y0.2Er0.2Tm0.2Yb0.2)2Zr2O7 is a competitive candidate for high reliability TBC materials.