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

(La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics were synthesized using the solid state reaction method and their thermophysical properties were investigated. All (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics were composed of the pure pyrochlore phase. The average thermal expansion coefficients of the (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics ranged from 9.54 to 9.78×10 −6 K −1 . The substitution of Yb 3+ and Er 3+ for La 3+ substantially reduced the thermal conductivity of La 2 Zr 2 O 7 . 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 (La 1−2 x Yb x Er x ) 2 Zr 2 O 7 ceramics for high temperature thermal barrier coatings.