Mechanical properties, thermophysical properties and electronic structure of Yb3+ or Ce4+-doped La2Zr2O7-based TBCs

First-principles calculations based on density functional theory are performed to investigate the cohesive energies, elastic modulus, Debye temperatures, thermal conductivities and density of states of La 2− x Yb x Zr 2 O 7 , La 2 Zr 2− x Ce x O 7 and La 2− x Yb x Zr 2− x Ce x O 7 ( x = 0.00, 0.25, 0.50, 0.75, 1.00) ceramics. The results show that Yb 3+ or Ce 4+ doped into La 2 Zr 2 O 7 reduce its elastic modulus, thermal conductivity and Debye temperature. Compared with La 2− x Yb x Zr 2 O 7 ( x ≠ 0.00),La 2 Zr 2− x Ce x O 7 compounds have better ductility and lower Debye temperature. The Debye temperature values of La 2 Zr 2− x Ce x O 7 ( x ≠ 0.00) compounds are in the range 485.0∼511.5 K. Among all components, the fluorite-type La 2− x Yb x Zr 2− x Ce x O 7 ( x = 0.75, 1.00) compounds exhibit better mechanical and thermophysical properties, and their thermal conductivity values are only 1.213∼1.246 W/(m∙K) (1073 K), which are 14.5∼16.7% lower than that of the pure La 2 Zr 2 O 7 . Thus, our findings open an entirely new avenue for TBCs. Yb 3+ or Ce 4+ doped into La 2 Zr 2 O 7 reduce its elastic modulus, thermal conductivity and Debye temperature. Additionally, La 2 Zr 2− x Ce x O 7 compounds have better ductility, lower thermal conductivity and Debye temperature than those of La 2− x Yb x Zr 2 O 7 . In all components, the fluorite-type La 2− x Yb x Zr 2− x Ce x O 7 ( x = 0.75, 1.00) are the most suitable for TBCs. In particular, the thermal conductivity values of La 2− x Yb x Zr 2− x Ce x O 7 ( x = 0.75, 1.00) compounds are only 1.213∼1.246 W/(m∙K)(1073 K), which are 14.5∼16.7% lower than that of undoped La 2 Zr 2 O 7 , respectively. • Thermal conductivity of Yb- and Ce-doped La 2 Zr 2 O 7 decreased significantly after pyrochlore.→fluorite phase transformation; • Yb 3+ or Ce 4+ doped into La 2 Zr 2 O 7 reduce its elastic modulus, thermal conductivity and Debye temperature. • La 2 ZrCeO 7 compound has better ductility and lower Debye temperature than those of LaYbZr 2 O 7 . • La 2- x Yb x Zr 2- x Ce x O 7 ( x =0.75, 1.00) compounds with thermal conductivity values of 1.213∼1.246 W/(m∙K) (1073K) are suitable for TBCs.