Abstract
Urea was added in the thermal formation systems of various rare earth phosphates, orthophosphate, pyrophosphate, polyphosphate, and ultraphosphates, prepared from rare earth compounds (oxide and carbonate) and phosphoric acid. The addition of urea gave rare earth orthophosphate larger specific surface area. In the formation systems of condensed phosphates, the addition of urea promoted the dehydration condensation reaction of phosphates. In cerium salts, which were expected to have the different thermal behavior from other rare earth phosphate because of exsistence of tetravelent cerium cation, the formation of tetravalent cerium phosphates was suppressed by the addition of urea.
