Formation and thermal properties of fluorite-pyrochlore composite structure in La_2(Zr_xCe_(1-x))_2O_7 oxide system

摘要

Rare-earth oxides of La_2(Zr_xCe_(1-x))_2O_7 for thermal barrier coatings (TBCs) are fabricated via a solid-state reaction at 1600 °C. As the phase formation, microstructure, and thermal properties of these oxides are examined, a fluorite-pyrochlore composite structure is found in the La_2(Zr_xCe_(1-x))_2O_7 system. This composite structure is composed of coarse Ce-rich fluorite and fine Zr-rich pyrochlore grains. From XRD and microstructural analysis, the lattice parameter and volume fraction of each phase are evaluated in order to obtain the intrinsic thermal conductivity value of composite-structured oxide with porosity calibration. The thermal conductivity of the composite structure is similar to that of pyrochlore La_2Zr_2O_7, which is attributed to phonon scattering by phase boundaries.