Synthesis, characterization and luminescent properties of needle-like lanthanide-doped orthorhombic Y5O4F7

Thermal annealing of YOH1.1F1.9 and YOH1.1F1.9: Ln3+ (Ln3+=Eu3+, Tb3+ and Gd3+) precursors in air gave access to synthesize yttrium oxyfluoride phosphors with well-preserved needle-like morphologies. The phase purities of samples strongly depended on the thermal annealing temperature. At 600 °C, pure Y5O4F7 with orthorhombic structure were obtained, as evidenced by powder X-ray diffraction measurement and chemical analysis. The interesting microstructure evolution of the annealed sample from well-organized nanoparticles on curly slices to microrod-bundle structure had been aroused by raising annealing temperature. The multicolor fluorescent emissions of Y5O4F7: Ln3+ phosphors were observed, e.g. ultraviolet emission for Gd3+, green emission for Tb3+ and red emission for Eu3+, which resulted from characteristic transitions of different lanthanide ions.