セリア及びその前駆体粒子の水熱合成

Abstract

Fine particles of ceria and its precursor were obtained from solutions of cerium salts in the presence of urea by heating under hydrothermal conditions at 120 to 180℃. The effects of the nature of the starting cerium (Ce(III) or Ce(IV)) salts, the concentration of urea, and hydrothermal treatment temperature on the composition, morphology, the crystal phase and crystallite size of synthesized particles were investigated. Ultra-fine CeO_2 particles were hydrothermally synthesized from 0.1mol・dm^<-3> cerium (IV) salts and their crystallite size was decreased from 20 to 10 nm with increasing urea concentration from 2 times to 8 times that of the. Ce^<4+> ion. On the other hand, two types of carbonate particles were formed from cerium (III) salts, and their crystal phase also significantly depended on the concentration of urea and treatment temperature. It changed gradually from orthorhombic to hexagonal with increasing urea concentration and treatment temperature.