Rare-Earth Zirconate Ceramics with Fluorite Structure for Thermal Barrier Coatings

A series of rare-earth zirconate Ln2Zr2O7 ceramics (Ln=Dy, Er, and Yb) with a fluorite structure (F-Ln2Zr2O7) were prepared by pressureless sintering from zirconia and rare-earth oxide powders at 1600°C for 10 h in air. The microstructure experiments were performed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The thermal conductivity and thermal expansion of these ceramics were evaluated using a steady-state laser heat-flux technique and high-temperature dilatometry, respectively. The XRD and SEM results demonstrate that Ln2Zr2O7 ceramics with a single fluorite phase are synthesized and no other phases are found. The results of thermal conductivity show that their thermal conductivities (1.3–1.9 W/(m·K), 20°–800°C) are as low as those of the referenced Ln2Zr2O7 ceramics (Ln=La, Nd, Sm, and Gd) with pyrochlore structure (P-Ln2Zr2O7). It is concluded that rare-earth zirconate ceramics with a fluorite structure can be considered as candidate materials for future thermal barrier coatings.