Enhanced green upconversion luminescence properties of Er3+/Yb3+ co-doped strontium gadolinium silicate oxyapatite phosphor

Upconversion Sr2(Gd.98-xEr.02Ybx)8Si6O26 (SGSO:2Er3+/xYb3+) 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:2Er3+/xYb3+ phosphors depicted submicron particles. The enhanced upconversion luminescence properties of SGSO:2Er3+/xYb3+ 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:2Er3+/xYb3+ 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.