Spherical SiO₂ @ GdPO₄ : Eu³⁺ Core–Shell Phosphors: Sol–Gel Synthesis and Characterization

Nanocrystalline GdPO₄ : Eu³⁺ phosphor layers were coated on non-aggregated, monodisperse and spherical SiO₂ particles by Pechini sol–gel method, resulting in the formation of core–shell structured SiO₂ @ GdPO₄ : Eu³⁺ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), time-resolved PL spectra and lifetimes were used to characterize the core–shell structured materials. Both XRD and FT-IR results indicate that GdPO₄ layers have been successfully coated on the SiO₂ particles, which can be further verified by the images of FESEM and TEM. Under UV light excitation, the SiO₂ @ GdPO₄ : Eu³⁺ phosphors show orange-red luminescence with Eu^{3+ 5}D₀–⁷F₁ (593 nm) as the most prominent group. The PL excitation and emission spectra suggest that an energy transfer occurs from Gd³⁺ to Eu³⁺ in SiO₂ @ GdPO₄ : Eu³⁺ phosphors. The obtained core–shell phosphors have potential applications in FED and PDP devices.