Synthesis and Characterization of Fluorite-Like Ce-Zr-Y-La-O Systems

Ce-Zr-O and Ce-Zr-Y-La-O materials obtained under various conditions and at varying component ratios are characterized. At Ce/Zr ≈ 1, a tetragonal phase that can hardly be distinguished from a cubic phase by X-ray diffraction forms in the ternary system. Raising the precipitation temperature favors the formation of two-phase systems. Promoting the Ce/Zr = 0.26–0.62 materials with both yttrium and lanthanum favors the formation of a single-phase specimen, namely, a (Ce, Zr, Y, La)O₂ fluorite-like solid solution at 600°C. This structure persists up to 1150°C. The specific surface area of the (Ce, Zr, Y, La)O₂ materials is primarily determined by their calcination temperature: S_sp = 50–80 m²/g at 600°C and 0.6–0.8 m²/g at 1150° C. The specimens calcined at 600°C are mesoporous, with uniformly sized pores of mean diameter 32 ± 2 Å, and have no micropores. According to TPR data, the specimens calcined at 600°C are reduced with hydrogen in two steps that can apparently be interpreted as surface and bulk reduction. The Ce/Zr = 0.26 and 0.40 specimens calcined at 1150°C are reduced in a single step, giving rise to TPR peaks at 707 and 686°C, respectively, and their degree of reduction increases with decreasing Ce/Zr.