Systematic studies on Sr4La6(SiO4)6M2:Eu3+ (M = F/Cl) phosphors: effects of the halogen anions on photoluminescence

Abstract

We successfully prepared Sr4La6(SiO4)6F2:Eu3+ (SLSOF:Eu3+) and Sr4La6(SiO4)6Cl2:Eu3+ (SLSOC:Eu3+) oxyapatite phosphors via the traditional solid-state method. The phosphors’ structure and photoluminescence properties were investigated by scanning electron microscope (SEM), X-ray powder diffraction (XRD), photoluminescence (PL) spectroscopy, ultraviolet–visible spectra and temperature-dependent emission spectra. Among them, the irregular morphology of SLSOF and SLSOC particles was displayed by SEM images, and the phase formation of both sets of phosphors was illustrated by XRD analysis. Additionally, PL spectra indicated that the phosphor could be efficiently excited by the near ultraviolet (NUV) light, and then emitted shining red light, agreeing well with that the calculated color coordinates are within the red region. Comparatively, the luminescence intensity of SLSOF:Eu3+ is higher than that of SLSOC:Eu3+ on the basis of the greater electronegativity of F−, which directly leads to the enhancement of 5D0→7F2 transition. The temperature-dependent emission spectra indicated that samples have excellent thermal stability. Internal quantum efficiency value of phosphors were calculated. These results indicated that the halogen anions of these Sr4La6(SiO4)6M2:Eu3+ play important roles in their PL properties and both phosphors have great potential to serve as red emitting phosphor for NUV white light emitting diodes.