The types, preparation methods, thermal and mechanical properties of rare earth hafnate materials and their corrosion behaviors exposed to low melting point silicate（CMAS） and high temperature water vapor are summarized. The previous investigations indicate that the rare earth hafnates have the characteristics of low thermal conductivity, excellent high-temperature phase stability and good resistance to CMAS corrosion, which shows a favorable application prospect in the field of thermal/environmental barrier coatings（T/EBCs）. However, in order to overcome the limitations of a single-phase rare earth hafnate exposed to water vapor corrosion and CMAS, it is still necessary to carry out systematic studies on multi-rare earth components/high-entropy rare earth hafnate in the future, and further clarify the mechanism of influence of lattice distortion caused by components on physical and chemical properties of materials. Moreover, the coupled control method of thermal, mechanical and chemical properties of hafnate with integrated functions such as thermal protection, water vapor corrosion resistance and CMAS resistance and their corresponding material preparation processes should be explored.

The corrosion behavior of environmental barrier coatings (EBCs) directly affects the service life and stability of ceramic matrix composite (CMC) structural parts in the aero-engines. The silicon carbide (SiC) whisker toughening phase and c-AlPO₄ bonding phase are firstly used to improve the service life of novel tri-layer Yb₂Si₂O₇/mullite/SiC EBCs in the burner rig test. The formation of penetrating cracks in Yb₂Si₂O₇/mullite/SiC coating caused the failure of coating at 1673 K. The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb₂Si₂O₇/mullite/SiC coating, and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide (C_f/SiC) samples for 360-min thermal cycles (24 times) with a weight loss of 6.19×10⁻³ g·cm⁻². Although c-AlPO₄ particles further improved the service life of SiC_w–mullite (SM) coating, the overflow of PO_x gas aggravated the formation and expansion of cracks in the Yb₂Si₂O₇ outer coating, and caused the service life of overall Yb₂Si₂O₇/c-AlPO₄–SiC_w–mullite (ASM)/SiC coating to be slightly lower than that of Yb₂Si₂O₇/SM/SiC coating. This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.