Effect of Powder Coating on Stabilizer Distribution in CeO2-Stabilized

The phase and microstructure relationship of 12 mol % CeO2-stabilized ZrO2 ceramics prepared from coated powder was in-vestigated using scanning electron microscopy (SEM), trans-mission electron microscopy (TEM), and energy-dispersed X-ray spectroscopy (EDS). As compared with the sample prepared with co-precipitated method, which exhibited a similar grain size distribution, the EDS analysis revealed that the powder coating induced a wide distribution of CeO2 solubility, which decreases monotonically with the increase of grain size. This variation of stabilizer content from grain to grain rendered many large grains in the monoclinic phase. Stronger cerium segregation to grain boundaries was observed between large grains, which often form thin amorphous films there. The inhomogeneous CeO2 distribution keeps more tetragonal ZrO2 grains close to the phase boundary to facilitate the transforming toughness. Addi-tion of an Al2O3 precursor in coated powders effectively raises the overall CeO2 stabilizer content in the grains and preserves more transformable tetragonal phase in the microstructure, which further enhanced the fracture toughness. The dependence of CeO2 solubility on grain size may be explained in a simple coating-controlled diffusion and growth process that deserves further investigation. I