Crystal phase, morphology evolution and luminescence properties of Eu³⁺ -doped BiPO₄ phosphor prepared using the...

A series of Bi_1-x Eu_x PO₄ phosphors was successfully prepared using an easy citric acid- assisted hydrothermal method. The effects of synthesis temperature, amount of citric acid, and Eu³⁺ concentration on the crystal phase, morphology, and luminescence properties were investigated. X-ray diffraction results revealed that BiPO₄ :Eu³⁺ formed a hexagonal phase at 80°C, although it transformed to a monoclinic phase when the hydrothermal temperature was increased to 160°C. Moreover, it was found that a small amount of Eu³⁺ doping and the addition of citric acid introduced no secondary or related phases. The morphologies of the samples varied from nanoparticles to spherical microparticles to polyhedrons after the synthesis temperature was adjusted. Particle size was controlled by adding different amounts of citric acid. Under 394 nm excitation, the Bi_0.95 Eu_0.05 PO₄ phosphor prepared at 160°C with 0.3 g of citric acid had excellent luminescence properties. A possible crystal growth mechanism during this reaction is proposed.