Sol–gel synthesis and photoluminescence properties of spherical SiO2@LaPO4:Ce3+/Tb3+particles with a core–shell structure

LaPO 4 :Ce 3+ and LaPO 4 :Ce 3+ , Tb 3+ phosphor layers have been deposited successfully on monodispersed and spherical SiO 2 particles of different sizes (300, 500, 900 and 1200 nm) through a sol–gel process, resulting in the formation of core–shell structured SiO 2 @ LaPO 4 :Ce 3+ / Tb 3+ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microcopy (SEM), transmission electron microscopy (TEM), and general and time-resolved photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO 2 @ LaPO 4 :Ce 3+ / Tb 3+ samples. The XRD results demonstrate that the LaPO 4 :Ce 3+ , Tb 3+ layers begin to crystallize on the SiO 2 templates after annealing at 700 °C, and the crystallinity increases on raising the annealing temperature. The obtained core–shell phosphors have perfectly spherical shape with a narrow size distribution, non-agglomeration, and a smooth surface. The doped rare-earth ions show their characteristic emission in the core–shell phosphors, i.e. Ce 3+ 5d–4f and Tb 3+ 5 D 4 – 7 F J ( J = 6–3) transitions, respectively. The PL intensity of the Tb 3+ increased on increasing the annealing temperature and the SiO 2 core particle size. The energy transfer process from Ce 3+ to Tb 3+ in SiO 2 @ LaPO 4 :Ce 3+ , Tb 3+ core–shell particles was studied using the time-resolved emission spectra.