• • High-density dislocations (10^8–10^10 mm^-2) introduced into ferroelastic YTaO4/Y3TaO7 composites via spark plasma sintering and heat treatment reduce thermal conductivity by acting as phonon scattering centers, while enhancing fracture toughness through crack deflection and energy dissipation, breaking the traditional trade-off.
• • The composite ceramics (YTaO4)1-x/(Y3TaO7)x with x=0.1–0.6 exhibit excellent lattice matching between monoclinic YTaO4 and Y3TaO7, enabling stable interfaces that contribute to improved mechanical integrity.
• • Ferroelastic domains at room temperature dissipate fracture energy via multiple mechanisms (crack deflection, domain switching, crack bridging), resulting in fracture toughness significantly higher than conventional ceramics, but grain boundary weakness previously limited performance; dislocation engineering strengthens grain boundaries.
• • The dual functionality of dislocations—phonon scattering and toughening—enables simultaneous optimization of thermal insulation and mechanical robustness, critical for long-period service in thermal barrier coatings under extreme conditions.