Low thermal conductivity in La2Zr2O7 pyrochlore with A-site partially substituted with equimolar Yb2O3 and Er2O3

(La1−2xYbxErx)2Zr2O7 ceramics were synthesized using the solid state reaction method and their thermophysical properties were investigated. All (La1−2xYbxErx)2Zr2O7 ceramics were composed of the pure pyrochlore phase. The average thermal expansion coefficients of the (La1−2xYbxErx)2Zr2O7 ceramics ranged from 9.54 to 9.78×10−6 K−1. The substitution of Yb3+ and Er3+ for La3+ substantially reduced the thermal conductivity of La2Zr2O7. The thermal conductivity decreased from 2.12 W m−1 K−1 for the composition with x=0 to 1.27 W m−1 K−1 for which with x=0.05 at 26 °C. In addition, the thermal conductivity for the composition with x= 0.05 was less sensitive to temperature variation, which ranged from 1.22 to 1.32 W m−1 K−1 in the measuring temperature range. These results suggested promising potential applications of the (La1−2xYbxErx)2Zr2O7 ceramics for high temperature thermal barrier coatings.