Crystal structure, energy transfer mechanism and tunable luminescence in Ce3+/Dy3+ co-activated Ca20Mg3Al26Si3O68 nanophosphors

Abstract

Ce3+, Dy3+ and Ce3+/Dy3+ co-doped Ca20Mg3Al26Si3O68 (CMAS) nanophosphors were synthesized via modified solution-combustion method. Sharp X-ray diffraction patterns confirmed the formation of pure crystalline phase of Ca20Al26Mg3Si3O68 as an orthorhombic crystal system having space group Pmmn. The phase purity of as synthesized material has allowed reliable structural parameters to be obtained from the Rietveld analysis of its powder diffraction pattern. The Ce3+, Dy3+ and Ce3+/Dy3+ emission at different lattice sites in CMAS host has been identified and discussed. Under ultra-violet (UV) excitation, optical properties and the energy transfer mechanism from Ce3+ to Dy3+ in CMAS: Ce3+/Dy3+ nanophosphors have been elaborated by photoluminescence spectroscopy. Also, the effects of doping and sintering temperature on the structure of prepared CMAS host samples have been investigated in detail. The Ce3+/Dy3+ concentration quenching mechanism due to multipole–multipole interaction has been studied and the critical energy-transfer distance was calculated to be 7.8Å. The band gap of the synthesized phosphors was calculated from diffuse reflectance spectra using the Kubelka–Munk function. A uniform layered structure network has been revealed in scanning electron microscopy images of the CMAS phosphor. Transmission electron microscopy results indicate nanocrystalline nature of synthesized phosphors. CMAS: 1m% Ce3+ and CMAS: 0.5m% Dy3+ nano-luminescent powders are promising candidate as a blue and blue–yellow emitting UV convertible phosphor for application in white light emitting diodes. By utilizing the energy transfer mechanism in present CMAS: Ce3+/Dy3+ nanophosphors, with an appropriate tuning of the activator content, these phosphors can exhibit great potential for white light emission, as single-emitting component phosphors in solid state lighting technology.