Preparation and thermophysical properties of (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2 (Zr 0.8Ce 0.2) 2O 7 ceramics for thermal barrier coatings

Abstract

Two kinds of rare earth zirconate (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 ceramics were prepared by solid state reaction at 1600 °C for 10 h. The phase compositions and microstructures, thermophysical properties of these materials were investigated. XRD results revealed that single phase (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 with pyrochlore structure were synthesized. The SEM results showed that the microstructures of these materials were dense and no other phases existed among the particles. With the temperature increasing, the thermal expansion coefficient (TEC) of the ceramic increased, while the thermal conductivity decreased. The thermal expansion coefficients of (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 are lower than that of Sm 2Zr 2O 7, the addition of CeO 2 resulted in a higher thermal expansion coefficient of (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 than that of 8YSZ and (Sm 0.5La 0.5) 2Zr 2O 7. However, the thermal expansion coefficient of (Sm 0.5La 0.5) 2Zr 2O 7 is lower than that of 8YSZ, it still fulfills the basic requirement of thermal barrier coatings. The thermal conductivities of (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 are much lower than that of Sm 2Zr 2O 7 because of the phonon scattering resulted by the doping of La 2O 3 or CeO 2, and the thermal conductivity of (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 is lower than of (Sm 0.5La 0.5) 2Zr 2O 7. These results imply that (Sm 0.5La 0.5) 2Zr 2O 7 and (Sm 0.5La 0.5) 2(Zr 0.8Ce 0.2) 2O 7 have potentials to be used as novel candidate materials for thermal barrier coatings in the future.