The mechanical and thermophysical properties of La2(Zr1−xCex)2O7 ceramics

The La2(Zr1−xCex)2O7 (x = 0, 0.3, 0.5, 1.0) powders were synthesized by coprecipitation-calcination method. The XRD results indicated that La2(Zr0.5Ce0.5)2O7 comprised of La2Ce2O7 and La2Zr2O7, whereas single phase La2(Zr0.7Ce0.3)2O7 with pyrochlore structure was synthesized at 1400 °C. The bulk La2(Zr1−xCex)2O7 (x = 0.3, 0.5, 1.0) were sintered at 1600 °C and showed excellent phase stability at 1450 °C. The La2Ce2O7 possessed the highest microhardness both in as-sintered state and after heat treatment at 1450 °C for different times, followed by La2(Zr0.5Ce0.5)2O7 and La2(Zr0.7Ce0.3)2O7. The La2(Zr0.5Ce0.5)2O7 had the highest fracture toughness of 3.8 ± 0.2 MPa m1/2 in as-sintered state, followed by La2(Zr0.7Ce0.3)2O7 (3.5 ± 0.2 MPa m1/2) and La2Ce2O7 (2.6 ± 0.3 MPa m1/2), which are much higher than that of La2Zr2O7 and 8YSZ. The sudden thermal expansion decrease of La2Ce2O7 was fully suppressed in La2(Zr0.7Ce0.3)2O7. The La2(Zr0.7Ce0.3)2O7 also had the lowest sintering rate of 1.13 × 10−7 s−1 at 1400 °C, as well as the lowest thermal conductivity of 1.06 Wm−1K−1 at 900 °C.