Mechanical Properties and Strengthening Mechanism of YbTa 3 O 9 With Double‐Perovskite Structure as a Potential Thermal Barrier Coating Material

YbTa 3 O 9 with a perovskite structure exhibits an extremely low thermal conductivity and a thermal expansion coefficient comparable to that of yttria‐stabilized zirconia (YSZ), rendering it a promising candidate material for next‐generation advanced thermal barrier coatings. Nevertheless, systematic investigations on the mechanical properties of YbTa 3 O 9 remain insufficient to date. In this work, dense YbTa 3 O 9 bulks were successfully fabricated via pressureless sintering route. The flexural strength and flexural modulus of YbTa 3 O 9 were systematically characterized through three‐point bending tests combined with the digital image correlation (DIC) technique, while its fracture work and fracture toughness were measured using the single‐edge notched beam (SENB) method. The results demonstrate that YbTa 3 O 9 possesses superior strength and toughness. Specifically, its flexural strength and fracture work are significantly higher than those of conventional YSZ ceramics. Microstructural analysis of the fractured SENB cross‐sections reveals that the excellent mechanical strength and toughness of YbTa 3 O 9 are closely associated with its in situ formed nanodomain structure. The nanoscale domain structure induces crack deflection and crack branching behavior during fracture, which effectively enhances the strength and toughness of the material. This study provides a solid foundation for the engineering applications of perovskite‐structured ReTa 3 O 9 tantalates as high‐performance thermal barrier coating materials.