Core–shell structured SiO 2@YVO 4:Dy 3+/Sm 3+ phosphor particles: Sol–gel preparation and characterization

Abstract

Spherical SiO 2 particles have been coated with YVO 4:Dy 3+/Sm 3+ phosphor layers by a Pechini sol–gel process, leading to the formation of core–shell structured SiO 2@YVO 4:Dy 3+/Sm 3+ particles. X-ray diffraction (XRD), Fourier-transform IR spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO 2@YVO 4:Dy 3+/Sm 3+ core–shell phosphors. The obtained core–shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 300 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (20 nm for one deposition cycle). The core–shell particles show strong characteristic emission from Dy 3+ for SiO 2@YVO 4:Dy 3+ and from Sm 3+ for SiO 2@YVO 4:Sm 3+ due to an efficient energy transfer from YVO 4 host to them. The PL intensity of Dy 3+ and Sm 3+ increases with raising the annealing temperature and the number of coating cycles.