Molten Salt Synthesis and Luminescent Properties of YVO₄:Ln (Ln = Eu³⁺, Dy³⁺) Nanophosphors

Eu³⁺ and Dy³⁺-doped YVO₄ nanocrystallites were successfully prepared at 400 °C in equal moles of NaNO₃ and KNO₃ molten salts. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spec-troscopy, transmission electronic microscopy (TEM), photoluminescence (PL) spectrum and lifetime were used to characterize the nanocrystallites. XRD results demonstrate that NaOH concentration and annealing temperature play important roles in phase purity and crystallinity of the nanocrystallites, the optimum NaOH concentration and annealing temperature being 6:40 and 400 °C respectively. TEM micrographs show the nanocrystallites are well crystallized with a cubic morphology in an average grain size of about 18 nm. Upon excitation of the vanadate group at 314 nm, YVO₄:Eu³⁺ and YVO₄:Dy³⁺ nanocrystallites exhibit the characteristic emission of Eu³⁺ and Dy³⁺, which indicates that there is an energy transfer from the vanadate group to the rare earth ions. Moreover, the structure and luminescent properties of the nanocrystallites were compared with their bulk counterparts with same composition in detail.