Thermal and oxygen transport properties of complex pyrochlore RE2InTaO7 for thermal barrier coating applications

Pyrochlore-type rare earth zirconate (RE2Zr2O7) has been considered as a new generation thermal barrier coating (TBC) material. We substitute Zr4+ with a pair of In3+ and Ta5+ in RE2Zr2O7 (RE = Pr, Nd, Sm, Eu, Gd), forming a complex pyrochlore material RE2InTaO7. Combined with the structural disordering, the thermal conductivities of RE2InTaO7 were progressively reduced to the amorphous limit. Phonon scattering due to the structural complexity and disordering was confirmed by the reduced phonon mean free path and further demonstrated by the broadened Raman modes. Meanwhile, the oxygen ion conductivities were reduced by two orders of magnitude compared with that of normal pyrochlore structure. This paper demonstrates the approach of structural complexing could simultaneously tune thermal and oxygen transport properties toward high-efficiency and durable TBC applications.