Sol-Gel Precursors and the Oxygen Storage Capacity of PrO y -ZrO 2 Materials

The gels derived from mixtures of Pr(O i C 3 H 7 ) 3 and Zr(O i C 3 H 7 ) 4 • i C 3 H 7 OH, upon hydrolysis and pyrolysis, furnish single-phase PrO y -ZrO 2 materials crystallized in the fluorite structure. These materials can be coated onto high-surface-area γ-alumina powders or deposited onto dense α-alumina coupons in the form of thin films from a solution of parent alkoxides modified with 2,4-pentanedione in THF. The fluorite structure of the PrO y -ZrO 2 in the films appears to be thermally stable in air up to 1200°C. Temperature-programmed-reduction (TPR) measurements show that the bulk PrO y -ZrO 2 material with a Pr. Zr molar ratio of 1:1 can store and release oxygen while that with a molar ratio of 1:3 cannot. The precursors play an important role in determining phase composition of the resulting PrO y -ZrO 2 material. A mixture of monoclinic and cubic or tetragonal phases was found in PrO y -ZrO 2 prepared from a new single-source heterometallic alkoxide, Pr 2 Zr 6 (μ 4 -O) 2 (μ-OAc) 6 (μ-O i Pr) 10 (O i Pr) 10 , whereas a mixture of cubic and tetragonal phases was present in PrO y -ZrO 2 made previously by coprecipitation from aqueous solutions of the metal nitrates.