Controlled synthesis and optical properties of BaFBr:Eu2+ crystals via ethanol/water solutions

Graphical abstract: A facile and cost-effective approach for the controlled synthesis of BaFBr:Eu2+ crystals is introduced. The structures and morphologies of the obtained products are affected by the amount of water and ethanol in the solvent mixtures. Highlights: ► Precipitation route for preparing BaFBr nano and micro crystals in water/ethanol solvent mixtures. ► Controlled growth of BaFBr nano crystals by tuning the volume ratio of Ethanol/water. ► Luminescence properties after annealing at 200 °C are investigated. ► Short lifetimes of photoluminescence and photostimulated luminescence in BaFBr:Eu2+ nano crystals are presented. ► Shortened lifetimes in BaFBr:Eu2+ nano crystals demonstrate that they are promising materials for use in X-ray imaging systems. -- Abstract: BaFBr:Eu2+ crystals with different structures were successfully fabricated via a simple precipitation method using ethanol/water mixtures as solvents. The amount of ethanol in the solvent mixtures played a significant role in the formation of final products, enabling the well-controlled growth of the BaFBr crystals. A possible formation mechanism was proposed based on the results of controlled experiments. The phases and morphologies of the resulting samples were systematically investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED) and elementary analysis. The optical properties of the annealed BaFBr:Eu2+ nano-cuboids were investigated using photoluminescence (PL), photo-stimulated luminescence spectroscopy (PSL) and kinetic decays. Faster decay behaviors demonstrate that these BaFBr:Eu2+ phosphors are promising materials for applications in optical storage fields. Furthermore, it is envisaged that this environmentally benign method can be extended to prepare other fluoride halides.