Characterisation of ceria–zirconia solid solutions after hydrothermal ageing Original Research Article

Ce1−xZrxO2 (x=0–0.84) solid solutions prepared by co-precipitation were characterised after calcination at 700 or 900°C, and after hydrothermal ageing at 1000 or 1200°C. The solid solutions were formed at 700°C, and crystallise as cubic or tetragonal phases depending on their compositions. Despite the rather high surface areas obtained after calcination at 700°C, the sintering is important at 900°C, and tremendous after hydrothermal ageing at 1000°C. For all compositions between 16 and 83 mol% ceria, complete de-mixing of the solid solutions into two phases was observed after ageing at 1200°C: one Zr-rich, tetragonal phase, and one Ce-rich, cubic phase. XPS and ISS measurements show that the phase separation takes place with surface enrichment in Zr, the Zr-rich phase being formed at the periphery of the particles, whereas the core is composed of the Ce-rich phase.