Synthesis and luminescence properties of highly uniform SiO2@LaPO4:Eu3+ core–shell phosphors

Abstract

Abstract SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors have been successfully synthesized by a one-step and economical wet-chemical route at low temperature. The as-obtained products were characterized by means of photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The SEM, EDS and XPS analysis indicate that SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors can only be synthesized in a pH range of 8–11 and the possible mechanism has been proposed. The XRD results demonstrate that the structure of LaPO 4 :Eu 3+ layers is transferred into monoclinic phase from hexagonal phase after annealing at 800 °C for 2 h. The SiO 2 @LaPO 4 :Eu 3+ phosphors show strong orange–red luminescence under ultraviolet excitation. The relative emission intensity of Eu 3+ increases with increasing the annealing temperature and the number of coating cycles, and the optimum concentration for Eu 3+ was determined to be 5 mol% of La 3+ in SiO 2 @LaPO 4 phosphors.