Structural characterization of ceria-zirconia powder catalysts prepared byhigh-energy mechanical milling: A neutron diffraction study

Neutron diffraction measurements were carried out on samples of CeO2-ZrO2 p owder catalysts prepared by high-energy mechanical milling. The formation o f solid solution was evidenced across the entire composition range examined . Quantitative phase evaluation by the Rietveld method indicated formation of tetragonal structure for low CeO2 content, whereas cubic solid solutions were the stable form at high CeO2 loading, In addition, a pseudocubic or t etragonal t " cell with axial ratio of unity and with internal deformation of the oxygen sublattice was observed at intermediate composition (50 mol% CeO2). Thermal annealing up to 1000 degrees C showed expansion of the unit cell parameters; an increase in the degree of tetragonality at the expense of cubic and monoclinic phase was observed for composition CexZr1-xO2 (x < 0.5).