Single-phase PrOy-ZrO2 materials and their oxygen storage capacity: A comparison with single-phase CeO2-ZrO2, PrOy-CeO2, and PrOy-CeO2-ZrO2 materials

High-surface-area PrOy-ZrO2 mixed oxide, crystallized in the cubic fluorite structure, is synthesized for the first time as a single-phase material ov er a wide range of composition by sol-gel processing. X-ray powder diffract ion shows that the material remains single phase even after thecal treatmen t In air to 900 degrees C. The oxygen storage capacity of PrOy-ZrO2, where praseodymium undergoes pr(3+) <-> Pr4+ interconversion, is assessed by temp erature-programmed reduction with H-2. The results show that there is littl e oxygen storage capacity unless the PrOy concentration exceeds 25 mol %. A comparison of oxygen storage capacity from similarly prepared single-phase CeO2-ZrO2, PrOy-CeO2, and PrOy-CeO2-ZrO2 materials is presented. Measureme nts of lattice parameter and reducibility suggest that there are preferred associations that lead to PrOy-ZrO2 and CeO2-ZrO2 rather than PrOy-CeO2 in the ternary mixed oxide. An evaluation of model Pd catalysts, using PrOy-Zr O2 and CeO2-ZrO2 as support materials, in functional tests approximating wa rmed-up, steady-state operation of an automotive catalyst, is also reported .