The enhanced toughness and growth kinetics in HfxTa2O2x+5 through modulated structure

Although HfxTa2O2x+5 shows great potential as a next-generation thermal barrier coating (TBC) material, the diversity of its potential modulated structures presents challenges in determining their mechanical properties. HfxTa2O2x+5 (x = 4, 6, 8) ceramics were successfully fabricated using the sol–gel method. Research on growth kinetics has indicated that grain boundary diffusion is the speed-controlling step. The activation energy increased with a larger modulated structure. In addition, the fracture toughness also increased from 1.98 MPa•m1/2 for Hf4Ta2O13 to 3.30 MPa•m1/2 for Hf8Ta2O21. Density functional theory calculations revealed that HfxTa2O2x+5 exhibited intrinsic ductility owing to the denser packing of atoms in its larger modulated structure. Thus, the tight-knit chemical bond net may contribute to a large surface energy. The results of this study provide deep insights into the toughening mechanism of modulated structures and pave the way for the design of next-generation TBCs.