Facile synthesis and color-tunable properties of BaLuF₅:Ce,Tb,Eu(Sm) submicrospheres via a facile ionic liquid/EG two-phase system

BaLuF₅:Ce,Tb,Eu(Sm) submicrospheres were synthesized via an ILs/ethylene glycol(EG) two-phase system. The crystalline phase, size, morphology, and luminescence properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra. The results show that 1-methyl-3-octylimidazolium hexafluorophosphate ([Omim]PF₆) was used as fluoride source and capping agent to tune morphology and size of the crystals. The formation mechanism has been supposed. Under the excitation of ultraviolet, the BaLuF₅:5%Ce³⁺,5%Tb³⁺, BaLuF₅:Eu³⁺, and BaLuF₅:5%Ce³⁺,5%Sm³⁺ exhibit green and red emission, which was derived from Tb³⁺, Eu³⁺, and Sm³⁺ emission. When codoping Ce³⁺, Tb³⁺, Sm³⁺ or Eu³⁺ together, multi-color emission can be realized. Furthermore, this synthetic route may have potential applications for fabricating other lanthanide fluorides.