Effects of H2O2 and SO4(2-) Species on the Crystalline Structure and Surface Properties of ZrO2 Processed by Alkaline Precipitation

6 pages, 8 figures, 2 tables.The preparation of ZrO2 by alkaline hydrolysis of ZrOCl2·8H2O, leads to an amorphous oxohydroxide precursor that upon calcination at temperatures higher than 350°C produces a system with mixed crystallographic phases (monoclinic and tetragonal). Preparation of this material by the same procedure but adding different molar ratios of H2O2 produces amorphous precursors (ZHPn) developing, mainly, the tetragonal crystal phase at the same calcination temperatures. The molar fraction of the phases seems to be dependent on the H2O2 molar ratio, thus indicating a direct relationship of this parameter with the crystallization behavior. At a surface level, preparation with H2O2 seems to retain NH4+ from the alkaline medium even after calcination at 500°C for 2 h. The sulfation process of these ZHPn samples also modifies the structural properties; in this case, the crystallization process is delayed at higher temperatures, but with the same crystallographic features of the nonsulfated series, the tetragonal phase becoming stable for temperatures up to 800°C.The authors acknowledge the subsidy received from the "Dirección General de Investigación Científica y Técnica" (DGICYT-Spain) Project PB93-0917, for supporting part of this work. We also gratefully acknowledge the "Consejería de Educación y Ciencia/Junta de Andalucía" (Spain). J.A.N. thanks the NATO Science Committee for a Linkage Grant (HTECH.LG 960967).Peer reviewe