Enhanced green upconversion luminescence properties of Er-3/Yb3+ co-doped strontium gadolinium silicate oxyapatite phosphor

Upconversion Sr-2(Gd-0.98-xEr(.02)Yb(x))(8)Si6O26 (SGSO:2Er(3+)/xYb(3+)) phosphor materials were synthesized using a citrate sol-gel process. X-ray diffraction patterns confirmed their hexagonal structure. Field emission scanning electron microscopy images of SGSO:2Er(3+)/xYb(3+) phosphors depicted submicron particles. The enhanced upconversion luminescence properties of SGSO:2Er(3+)/xYb(3+) phosphors were analysed as a function of Yb3+ ion concentration and laser power. The energy transfer induced enhanced emission of the Er3+/Yb3+ ions co-doped SGSO phosphors was ascribed to multi-phonon relaxation. The calculated chromaticity coordinates of the SGSO:2Er(3+)/xYb(3+) phosphors showed emissions could be tuned by changing Yb3+ ion concentration. Optimized sample exhibited the chromaticity coordinate values near to the ultra-high definition television standard green emission coordinates.