Thermal expansion and fracture toughness of (RE0.9Sc0.1)2Zr2O7 (RE=La, Sm, Dy, Er) ceramics

(RE0.9Sc0.1)2Zr2O7 and pure RE2Zr2O7 (RE=La, Sm, Dy, Er) compounds were synthesized by a chemical-coprecipitation and calcination method, and their phase structure, thermal expansion behavior and fracture toughness were investigated. Compared with pure RE2Zr2O7, (La0.9Sc0.1)2Zr2O7 and (Sm0.9Sc0.1)2Zr2O7 exhibited larger lattice parameters mainly due to the presence of Sc3+ interstitial ions, while (Dy0.9Sc0.1)2Zr2O7 and (Er0.9Sc0.1)2Zr2O7 had smaller lattice parameters, might attributable to the substitution of Sc3+ for RE3+. With the addition of 10 mol% Sc2O3, the thermal expansion coefficients of La2Zr2O7 and Sm2Zr2O7 were obviously enhanced, while those of Dy2Zr2O7 and Er2Zr2O7 decreased, which was considered to have close relationship with the solid-solution mechanisms of Sc2O3 in (RE0.9Sc0.1)2Zr2O7. 10 mol% Sc2O3 doping benefited the fracture toughness of (RE0.9Sc0.1)2Zr2O7 (RE=La, Sm, Dy, Er), which could be attributed to the increased cohesive energy due to the lattice distortion.