Roles of fluorine and annealing on optical and structural properties of Nd:YF3 phosphor

The optical and structural properties of Nd:YF3 phosphors, synthesized by precipitation reaction using ethylene glycol solvent, were investigated. The Y:F molar ratio of precursors, where NH4F was employed as the fluorine source, was varied to prevent oxygen contamination during nucleation of the particles and to improve the photoluminescence efficiency. Structural investigations were carried out by means of X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray techniques. Samples prepared using precursors in stoichiometric proportion presented orthorhombic YF3 structure. The use of fluorine source in excess promoted formation of NH4Y2F7 crystalline phase, which was decomposed into YF3 after annealing at 400 °C for 1 h. Emission spectra of samples thermally treated enhanced by over 50 times compared with the as prepared. The results obtained show the role of fluorine excess associated with thermal annealing to obtain YF3 with improved features.