Superior Resistances to High‐Temperature Treatment and Ablation of A 6 B 2 O 17 (A = Zr, Hf; B = Nb, Ta) Multicomponent Ceramics

Multicomponent oxide ceramics yield great promises in next‐generation thermal protection systems according to their high potential for thermal stability and ablation resistance, but their protective mechanisms remain unclear. In this study, the five multicomponent A 6 B 2 O 17 (A = Zr, Hf; B = Nb, Ta) oxide ceramics with different atomic concentrations, respectively, at A‐ and B‐sites, were prepared via a solid‐state reaction with a rapid cooling process. Their phase, structural evolutions, and the properties under high‐temperature treatment and dynamic ablations were investigated to reveal thermal stability and anti‐ablation mechanisms. Only the (Hf 1/2 Zr 1/2 ) 6 (Ta 1/2 Nb 1/2 ) 2 O 17 with equal molar ratio both at A‐ and B‐sites maintained the A 6 B 2 O 17 phase after heat treatment at 1773 K for 25 h; the other samples underwent phase separation behaviors. In addition, the (Hf 3/4 Zr 1/4 ) 6 (Ta 2/3 Nb 1/3 ) 2 O 17 ceramic showed excellent ablation resistance (∼2500 K, 100 s) with the thinnest oxide layer. This property is attributed to the formation of “skeleton‐filler phase” protective composite layer, as the (Zr, Hf)O 2 “skeleton” owns high melting point and low volatility to resist thermal gas erosion, and the A n B 2 O 2n+5 family fills defects and hinders the penetrations of O 2 . This study expects to offer design for advanced thermal barriers suitable for the next‐generation hypersonic vehicles and reusable spacecraft.