Cerium oxide nanoparticles were synthesized by using the Forced Thin-Film Type Reactor (FTFR). A reaction region which promotes forced diffusion is formed in FTFR. Aqueous solutions of cerium (III) nitrate and a diammonium cerium (IV) nitrate were prepared as raw materials. The mixing ratio of trivalent and tetravalent cerium ions in the solutions were 100:0, 50:50 and 0:100. A sodium hydroxide aqueous solution was added to the cerium solutions to precipitate cerium oxide. The nanoparticles which have an average diameter of 3 nm and 15 nm were synthesized in a tetravalent cerium ion solution and a trivalent cerium ion solution, respectively. The different solubility of cerium (III) and cerium (IV) hydroxide which acted as a crystal nucleus was assumed to be the cause of the different size of the nanoparticles. The measurement results of average particle size determined by TEM observation and crystallite size determined by XRD were suggested that the synthesized cubic cerium oxide nanoparticles were single crystals.
