Low Thermal Conductivity of Rare-Earth Zirconate-Stannate Solid Solutions (Yb2Zr2O7)1-x(Ln2Sn2O7)x (Ln = Nd, Sm)

Dense monoliths of rare-earth zirconate-stannate solid solutions (Yb2Zr2O7)(1-x)(Ln(2)Sn(2)O(7))(x) (Ln = Nd, Sm) were prepared by solid-state reaction. Characterized by XRD, Raman, SEM, and TEM, a double-phase structure of Yb2Zr2O7-rich fluorite and Nd2Sn2O7-rich pyrochlore was observed in the specimens of x = 0.4 and 0.5 of (Yb2Zr2O7)(1-x)(Nd2Sn2O7)(x) series while complete solid solutions were formed within the whole composition range of (Yb2Zr2O7)(1-x)(Sm2Sn2O7)(x) series. Except for the defect phonon scattering, lattice softening caused by order-disorder phase transformation between pyrochlore and fluorite structures also plays an important role in minimizing the thermal conductivity. Low thermal conductivity with positive temperature dependence is achieved in both the series. Considering the structure stability and low thermal conductivity, rare-earth zirconate-stannate solid solutions may be promising materials for thermal insulating applications, such as thermal barrier coatings.