Transactions of the INDIAN CERAMIC SOCIETY Vol. 62 2003
Ceria Powders by Homogeneous
Precipitation Technique
S. Ramanathan and S. K. Roy
Pages : 88-91
DOI :10.1080/0371750X.2003.11012082
Abstract
Formation of precursors for ceria by two homogeneous precipitation reactions – (cerium chloride + urea at 95°C – called reaction A and cerium chloride + hexamethylenetetramine at 85°C – called reaction B) – has been studied. The variation of size of the colloidal particles formed and the zeta potential of the suspensions with progress of reactions exhibited similar trends for both the precipitation processes. Particle size increased from 100 to 300 nm with increasing temperature and extent of reaction. The zeta potential was found to decrease with increasing extent of precipitation in the pH range of 5 to 7. Filtration and drying led to agglomeration of the fine particles in case of the precursor from reaction B. The as-formed precursors were crystalline – a basic carbonate in case of reaction A and hydrous oxide in case of reaction B. It was found that nano-crystalline ceria powders (average crystallite size ~10 nm) formed above 400°C from both these precursors. The agglomerate size (D50) of the precursors and ceria powders formed after calcination at 600°C varied from 0.7 to 3 µm. Increasing calcination temperature up to 800°C, increased the crystallite size (50 nm). The zeta potential variation with pH and concentration of an anionic dispersant (calgon) for the ceria powders formed was studied to determine the ideal conditions for suspension stability. It was found to be maximum (i.e., the suspensions stable) in the pH range of 3 to 4 or calgon concentration of 0.01 to 0.1 weight percent.
