Breaking the Trade-Off Relationship Between Thermal Conductivity and Toughness of Ferroelastic Oxide Ceramics via a High-Density Dislocation Strategy.

Abstract

The trade-off relation between thermal conductivity and fracture toughness limits applications of brittle ceramic thermal insulation materials, and we propose that the high-density dislocation engineering acts as an effective strategy to synergistically reduce thermal conductivity and enhance toughness. The spark plasma sintering (SPS) and heat treatments introduce high-density dislocations (10⁸∼10¹⁰ mm^-2) into the ferroelastic YTaO₄/Y₃TaO₇ ceramic composites as thermal insulation materials. The effects of high-density dislocations on reducing thermal conductivity and enhancing toughness are elucidated from the phonon relaxation time and crack propagation behaviors, respectively. The high-density dislocations produce large lattice strains to reduce phonon relaxation time, and the lowest thermal conductivity reaches 1.32 W·m^-1·K^-1. The interfacial enhancements, ferroelastic domains, and high-density dislocations synergistically boost the toughness to 5.0 MPa·m^1/2, and the increment is higher than 50%. The effects of high-density dislocations on toughness and thermal conductivity are revealed from an atomic scale, and the proposed high-density dislocation strategy breaks the trade-off relationship between thermal conductivity and toughness for brittle ceramic thermal insulation materials.