Heather Bradshaw

Dependency of the Oxygen Storage Capacity in Zirconia–Ceria Solid Solutions upon Textural Properties

The oxygen storage capacity of Ce0.2Zr0.8O2 solid solutions, prepared by different synthesis routes and aged at 1000°C, is investigated by means of temperature-programmed reduction, total- and dynamic-OSC measurements. The use of CO and H2 as reducing agent is compared under dynamic conditions. It is observed that the dynamic OSC is critically dependent on sample pre-treatment and the nature of the reducing agent in the texturally unstable sample. In contrast, on a thermally stable Ce0.2Zr0.8O2 only minor effects of the pre-treatment upon dynamic OSC are noticed.

A rationale for the development of thermally stable nanostructured CeO2-ZrO2-containing mixed oxides

CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermally treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.

Hydrothermal crystallisation of doped zirconia: An in situ X-ray diffraction study

Energy-dispersive (X-ray) diffraction has been used on a third generation synchrotron source to study, in situ, the hydrothermal crystallisation of zirconia from the pre-cursor hydroxide under autoclave conditions. Because the sample and enclosure are highly absorbing, it is necessary to collect data at high energy so that meaningful Avrami-kinetics parameters can be determined over the temperature range of 200–250 °C. A clear lowering of the activation energy for crystallisation is observed when using cerium-doped materials.