Integrating toughness and thermal insulation in oxide ceramics
The advancement of extreme-condition equipment, such as hypersonic vehicles and next-generation gas turbine engines, imposes stringent requirements on thermal barrier materials, particularly high fracture toughness and low thermal conductivity. However, these properties are often mutually exclusive in oxide ceramics due to their intrinsic ionic and covalent bonding. Conventional strategies to reduce thermal conductivity, such as introducing point defects or porosity, typically degrade mechanical properties, while toughening methods like second-phase or phase transformation toughening can adversely affect thermal transport. Rare earth tantalates and niobates, which exhibit ferroelastic phase transitions, offer promise for ultra-high-temperature applications (>1500°C) due to their unique domain structures that enhance toughness. Yet, weak grain boundary bonding limits the full potential of ferroelastic toughening. Li et al. proposed a high-density dislocation engineering strategy to overcome this trade-off. By introducing dislocations with densities of 10^8–10^10 mm^-2 into (YTaO4)1-x/(Y3TaO7)x (x=0.1–0.6) composite ceramics via spark plasma sintering and subsequent heat treatment, they achieved significant reductions in thermal conductivity through phonon scattering while simultaneously enhancing fracture toughness via crack deflection and energy dissipation. This work successfully decouples thermal and mechanical performance, offering a new paradigm for microstructural design in thermal protection materials.