Preparation And Photoluminescence Of Rare-earth Doped Slilican Phosphors For White Leds

Rare-earth doped silicates phosphors were prepared by high temperature solid state reaction (SSR) and Pechini-sol-gel route, respectively. Using X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and fluorescent spectrophotometer, the influences of different doping ions including alkaline-earth metal ions and rare-earth ions, and preparing methods on phase compositions, microstructures and optical properties of silicates phosphors were studied. Experimental result show: (â…°) Comparing with SSR, Pechini-sol-gel route synthesized pure single phase phosphors with uniform phosphor particles and beneficial spherical shape. (â…±) Ba²⁺-doped Sr₂SiO₄:Eu²⁺ phosphors (Ba_xSr_2-x-ySiO₄:Euy2+) show two intense emission bands at green and yellow regions of spectrum, originated from Eu²⁺ ions accommodated at two different sites in the host crystal, whose peaks depend on the concentrations of Ba²⁺ and Eu²⁺ ions. Additional, Ba²⁺-doping favored the stabilization ofα′-Sr₂SiO₄ phase. Intense and broad excitation spectra and emission spectra were obtained by doping Ca²⁺ or Ba²⁺ ions in Li₂SrSiO₄:Eu²⁺ phosphor, which show blue emitting and yellow emitting in chromaticity diagram, respectively. (â…²) The energy transfer from Ce3+ to Eu²⁺ (Ce→Eu) was demonstrated to be the type of electric dipole-dipole interaction in the Eu²⁺ and Ce3+ codoped Li₂SrSiO₄ phosphor. There were broad blue and yellow emissions peaked at 400 nm and 570 nm, respectively. It was observed that Li₂SrSiO₄:0.5%Ce3+,0.75%Eu²⁺ displayed the highest emission intensity, and higher concentration of Eu²⁺ resulted in concentration quenching.