Mechanical and thermal properties of fine-grained quasi-eutectoid (La1−xYbx)2Zr2O7 ceramics.

A 2 B 2 O 7 -type rare earth zirconates have been intensively investigated as potential thermal barrier coating (TBC) materials due to their low thermal conductivities and high stability at high temperature. In this work, mixing La 3+ and Yb 3+ with a large difference in atomic radii at A site formed a quasi-eutectoid mixture of La 2 Zr 2 O 7 -rich pyrochlore phase and Yb 2 Zr 2 O 7 -rich fluorite phase. The competition between these two phases in grain growth effectively reduces the grain size down to 0.8–1 μm, giving rise to improved mechanical properties comparing with the single-phase materials, including a higher hardness, a higher fracture toughness and a lower elastic modulus. Furthermore, a significantly low thermal conductivity was found, as the small and heavy Yb 3+ ions that dissolve in the La 2 Zr 2 O 7 -rich pyrochlore could “rattle” in the lattice and strongly scatter the heat-carrying phonons. Considering the comprehensively improved mechanical and thermal properties, the quasi-eutectoid (La 1− x Yb x ) 2 Zr 2 O 7 ceramic can be considered as a potential TBC material. [ABSTRACT FROM AUTHOR]