Formation and thermal properties of fluorite-pyrochlore composite structure in La2(ZrxCe1 − x)2O7 oxide system

Rare-earth oxides of La2(ZrxCe1 − x)2O7 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 La2(ZrxCe1 − x)2O7 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 La2Zr2O7, which is attributed to phonon scattering by phase boundaries.

Research highlights
► La2(ZrxCe1 − x)2O7 composite oxide.
► Oxides with low thermal conductivity for thermal barrier coatings.
► LCZ (x = 0.5) composition forms a fluorite-pyrochlore composite structure.
► The low thermal conductivity of LCZ is due to phonon scattering by phase boundaries.