Redoxhydrothermal synthesis of cerium phosphate microspheres with different architectures

Abstract

Uniform CePO₄ microspheres are first synthesized via a highly efficient redox hydrothermal (RHT) route using unconventional tetravalent Ce(SO₄)₂·4H₂O as the cerium source. Products obtained at 150 °C for 2h are hexagonal crystalline CePO₄ microspheres with diameters ranging from 2 to 5 μm. By tuning the hydrothermal reaction time from 0 to 96 h, the morphologies of the obtained products undergo evolution from rodlike to spherelike and then to lamellar spherelike and lamellar star-shaped particles, accompanied by the phase transition from monoclinic Ce(H₂O)(PO₄)_3/2(H₃O)_1/2(H₂O)_1/2 to pure hexagonal CePO₄ and then to mixed phases of hexagonal and monoclinic CePO₄. A possible growth mechanism based on dissolution–recrystallization was proposed. The photoluminescence properties were investigated and these CePO₄ microspheres exhibit a narrower emission than that of CePO₄ nanoparticles. In addition, Ln³⁺ (Ln = Eu, Dy, and Tb) doped CePO₄ microspheres were also prepared, and their photoluminescent properties were studied.