Structural evolution and thermal conductivities of (Gd1−xYbx)2Zr2O7 (x=0, 0.02, 0.04, 0.06, 0.08, 0.1) ceramics for thermal barrier coatings

(Gd1−xYbx)2Zr2O7 (x=0, 0.02, 0.04, 0.06, 0.08, 0.1) compounds were synthesized by solid state reaction, and their phase structure and thermal conductivities were investigated. (Gd1−xYbx)2Zr2O7 (x=0, 0.02, 0.04, 0.06) exhibited pyrochlore structure, while (Gd1−xYbx)2Zr2O7 (x=0.08, 0.1) fluorite phase. The ordering degree of (Gd1−xYbx)2Zr2O7 (x=0, 0.02, 0.04, 0.06) pyrochlores decreased with increasing the Yb2O3 content. Among the (Gd1−xYbx)2Zr2O7 ceramics investigated, (Gd0.94Yb0.06)2Zr2O7 yielded the lowest thermal conductivity of ~1.14 W/mk at 800 °C, which was nearly 25% lower than that of Gd2Zr2O7. The structural disorder could cause the initial decrease in the thermal conductivity, and the reduced complexity of crystal structure resulting from the pyrochlore-fluorite phase transformation might contribute to the increased thermal conductivity.