Each rare earth compound (rare earth element; R = La, Ce, and Nd, anion; oxide, carbonate, chloride, nitrate, sulfate, oxalate, and fluoride) was mixed with (NH4)(2)HPO4 or H3PO4 in P/R = 1, 3, and 5, and heated in air. The resulting salts were analyzed by TG-DTA, XRD and FT-IR. CePO(4.)nH(2)O was not formed in the system of CeO2-H3PO4. However, this phosphate was synthesized in the systems of Ce(NO3)(3).6H2O-(NH4)(2)HPO4, Ce-2(CO3)(3).8H2O-, CeCl3.7H(2)O-, and Ce(NO3)(3).6H(2)O-H3PO4. The crystallinity Of CePO4.nH(2)O was high in the systems of CeCl3.7H(2)O-, and Ce(NO3)(3).6H(2)O-H3PO4. In P/Ce = 1, formation of CeO2 was observed in the systems of Ce-2(CO3)(3).8H(2)O-, CeCl3.7H(2)O-, and Ce-2(C2O4)(3).9H(2)O-(NH4)(2)HPO4. (C) 2002 Elsevier Science B.V. All rights reserved.