Investigations on the mechanical and thermal properties of multicomponent dual-phase rare-earth zirconate ceramics

In this work, a series of multicomponent rare-earth zirconate (RE 2 Zr 2 O 7 , RE=La, Nd, Sm, Eu, Gd or Yb) ceramics were synthesized using solid-state reaction method. The phase stability and key factors affecting the thermal conductivity and mechanical performances were investigated. These materials possess pyrochlore-fluorite dual-phase structure and show excellent high-temperature phase stability. (La 1/2 Yb 1/2 ) 2 Zr 2 O 7 displays a lower amorphous-like thermal conductivity (1.39–1.67 Wm −1 K −1 , 25–1000 °C), while other specimens present a 1/T-like dependence at low temperatures. (La 1/5 Nd 1/5 Sm 1/5 Gd 1/5 Yb 1/5 ) 2 Zr 2 O 7 exhibit higher hardness (11.37 ± 0.35 GPa) and fracture toughness (2.10 ± 0.11 MPa·m 1/2 ) in comparison with others. Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase RE 2 Zr 2 O 7 ceramics, while the influence of configurational entropy is more significant for mechanical properties. A synergistic increase in configurational entropy and size disorder is an effective strategy to enhance the comprehensive performance of multicomponent dual-phase rare-earth zirconates. • A series of dual-phase medium- and high-entropy RE 2 Zr 2 O 7 ceramics were tailored and synthesized. • Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase rare-earth zirconates. • Entropy is a more effective descriptor than size disorder for influencing the mechanical properties of these materials.