Systematic studies on Sr 4 La 6 (SiO 4) 6 M 2 :Eu 3+ (M = F/Cl) phosphors: effects of the halogen anions on photoluminescence

Abstract

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. We successfully prepared Sr 4 La 6 (SiO 4 ) 6 F 2 :Eu 3+ (SLSOF:Eu 3+ ) and Sr 4 La 6 (SiO 4 ) 6 Cl 2 :Eu 3+ (SLSOC:Eu 3+ ) 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:Eu 3+ is higher than that of SLSOC:Eu 3+ on the basis of the greater electronegativity of F − , which directly leads to the enhancement of 5 D 0 → 7 F 2 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 Sr 4 La 6 (SiO 4 ) 6 M 2 :Eu 3+ 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.