Thermal and crystallization behaviour of 8YSZ–CeO 2 system

Abstract

The effect of the addition of ceria (0–100%) on the thermal behaviour and crystallization of yttria cubic-stabilised zirconia powders prepared by a “soft” co-precipitation method was investigated in detail using thermogravimetry coupled with differential scanning calorimetry (TG–DSC) and X-ray diffraction (XRD). It was shown that the synthesized powders after drying constitute a mixture of pure ceria and (ZrYCe)Ox solid solution with a reduced ceria content. The synthesized powders after drying with ceria contents up to 20 mol.% are amorphous. Their crystallization in the temperature range of 623–873 K is accompanied by two exothermal effects, which can be explained by the crystallization of (ZrYCe)Ox solid solution with a reduced ceria content and the incorporation of ceria into this matrix, respectively. The powders with a ceria content above 20 mol.% are already crystallized after drying, and a solid solution with equilibrium composition of (ZrYCe)Ox is formed during heating to 873 K. At temperatures above 873 K, all investigated powders form homogeneous (ZrYCe)Ox solid solutions with face-centred cubic, fluorite type structure, without any apparent segregation of ceria. The (ZrYCe)Ox lattice parameter was found to be a function of ceria content according to Vegard's law.