Luminescent properties and energy transfer mechanism from Tb3+ to Eu3+ in single-phase color-adjustable Sr3MgSi2O8:Eu3+,Tb3+ phosphor prepared by the sol-gel method

A series of single-phase color-adjustable Sr3MgSi2O8:Eu3+,2Tb3+ phosphors were synthesized with the application of sol-gel method. The crystal structure, luminescence characteristics, fluorescence lifetime, energy transfer mechanism and thermal stability of phosphors were investigated. The results show that the emission spectrum of Sr3−x−yMgSi2O8:xEu3+,yTb3+ compose both the 5D4→7F5 transition of Tb3+ and the 5D0→7F1, 5D0→7F2 transition of Eu3+ at the excitation wavelength of 238 nm. The optimal doping concentration of Tb3+ was determined to be 2% when concentration quenching effect was comprehensively considered. On the basis of the energy transfer of Tb3+→Eu3+, the emission peak intensity of Eu3+ increases and that of Tb3+ decreases with the rising Eu3+ concentration. The unidirectional energy transfer efficiency of Tb3+→Eu3+ reaches 89.4% when the Eu3+ doping concentration is 8%. On the basis of Dexter's theory, the major mechanism of energy transfer lies in the electric dipoles interaction between Tb3+ and Eu3+. With an activation energy of 0.309 eV, Sr2.95MgSi2O8:3%Eu3+,2%Tb3+ phosphors enjoys good thermal stability. Its color coordinate diagram indicates that the luminous colors of phosphors can be customized from red to orange, then to green with the changing doping concentrations of Eu3+ and Tb3+. Based on Sr3MgSi2O8:Eu3+,Tb3+ phosphors has a good matchability with ultraviolet and near-ultraviolet LED chips, so it can be considered that Sr3MgSi2O8:Eu3+,Tb3+ phosphors have good application potential in the field of ultraviolet and near-ultraviolet white light emitting diodes.