Fabrication and optical properties of core–shell structured spherical SiO 2@GdVO 4:Eu 3+ phosphors via sol–gel process

Abstract

Europium-doped nanocrystalline GdVO 4 phosphor layers were coated on the surface of preformed submicron silica spheres by sol–gel method. The resulted SiO 2@Gd 0.95Eu 0.05VO 4 core–shell particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, low voltage cathodoluminescence (CL), time resolved PL spectra and kinetic decays. The XRD results demonstrate that the Gd 0.95Eu 0.05VO 4 layers begin to crystallize on the SiO 2 spheres after annealing at 600 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have spherical shape, narrow size distribution (average size ca. 600 nm), non-agglomeration. The thickness of the Gd 0.95Eu 0.05VO 4 shells on the SiO 2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). PL and CL show that the emissions are dominated by 5D 0– 7F 2 transition of Eu 3+ (618 nm, red). The PL and CL intensities of Eu 3+ increase with increasing the annealing temperature and the number of coating cycles. The optimum concentration for Eu 3+ was determined to be 5 mol% of Gd 3+ in GdVO 4 host.