Synthesis and photoluminescence of core–shell structured spherical SiO2@YPO4:Tb3+ phosphors via sol–gel process

Monodispersed SiO2@YPO4:Tb3+ core–shell submicrospheres were prepared through a simply homogeneous sol–gel method. The resulted SiO2@YPO4:Tb3+ core–shell particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence spectra (PL) and kinetic decays. The XRD results demonstrate that the YPO4:Tb3+ layers begin to crystallize on the SiO2 spheres after annealing at 500 °C and the crystallinity increases with raising the annealing temperature. The FTIR spectra show that the YPO4:Tb3+ shell has linked to the silica surface through forming a Si–O–Y bond. SEM and TEM analysis indicate that SiO2@YPO4:Tb3+ core–shell submicrospheres have the regular microstructures and uniform size distributions. The emission spectra of the obtained submicrospheres are dominated by 5D4–7F5 transition of Tb3+ (545 nm, green), and the emission intensities of Tb3+ increase with increasing the annealing temperatures and the number of coating cycles. The optimum concentration for Tb3+ was determined to be 5 mol % of Y3+ in YPO4 host.