SYNTHESIS OF PLATE-LIKE CERIUM PHOSPHATES AND THEIR PHOTOCHEMICAL PROPERTIES VIA SOFT CHEMICAL REACTIONS

Plate-like cerium phosphates have attracted attention because of their unique UV-shielding ability with low photocatalytic activity and excellent comfort when applied on skin. Plate-like hydrated cerium phosphate, Ce2(PO4)2HPO4·H2O, ca 3 μm in diameter, was obtained by the hydrothermal reaction of Ce(SO4)2 in H3PO4 aqueous solution at 200 °C for 3 h. Ce2(PO4)2HPO4·H2O transformed to CeP2O7-CePO4, mixture around 700 °C with the transcription of plate-like morphology. Plate-like CePO4 and CeP2O7 were also synthesized as single phase by heating plate-like Ce2(PO4)2HPO4·H2O with cerium hydroxide and NH4H2PO4, respectively. Plate-like cerium phosphates showed excellent comfort, absorption ability of UV-light and lower oxidation catalytic activity than undoped ceria. The UV-shielding ability of them was in the order Ce2(PO4)2HPO4·H2O > CeP2O7 > CeP2O7-CePO4 mixture > CePO4 > K0.8Li0.266Ti1.734O4.