Enhanced thermal expansion and fracture toughness of Sc2O3-doped Gd2Zr2O7 ceramics

(Gd1−xScx)2Zr2O7 (x=0, 0.025, 0.05, 0.075, 0.1, 0.2) ceramics were synthesized by chemical co-precipitation and calcination and their phase structure, thermal expansion behavior and mechanical properties were investigated. (Gd1−xScx)2Zr2O7 (x=0, 0.025, 0.05, 0.075) exhibited pyrochlore structure. The ordering degree decreased and the lattice parameter increased with increasing the Sc2O3 content, but high Sc2O3 doping led to a pyrochlore-fluorite phase transformation and to a decrease in the lattice parameter. Among the (Gd1−xScx)2Zr2O7 ceramics investigated, (Gd0.925Sc0.075)2Zr2O7 yielded the largest thermal expansion coefficient (TEC). The structural disorder and lattice expansion could cause the initial increase in the TEC, and the decrease in the lattice parameter might contribute to the reduced TEC. Increasing Sc2O3 content benefited the fracture toughness of (Gd1−xScx)2Zr2O7, which could be attributed to the increased cohesive energy due to the lattice distortion and structural disorder.