The sensitized luminescence and tunable color of single-component Sr2MgSi2O7:Bi3+/Sm3+/Tb3+ phosphor via energy transfer for white-light emitting diodes

A series of single-phase blue-to-red tunable-color emitting and excellent green-emission Sr2MgSi2O7:Bi3+, Sm3+/Tb3+ phosphors have been synthesized by high temperature solid state reaction. The crystal structure of Sr2MgSi2O7 and the crystallographic sites of Bi3+, Sm3+ and Tb3+ ions in the host have been identified through the crystallographic data from Rietveld refinements. The luminescent properties of Sr2MgSi2O7:Bi3+/Sm3+/Tb3+ phosphors were investigated and the Bi3+, Sm3+ or Tb3+ single doped samples exhibit blue, orange-red and green emissions, originating from the 3P1→1S0 transition of Bi3+, the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2) transitions of Sm3+ and the 5D4→7FJ (J = 6, 5, 4, 3) multiplet transitions of Tb3+, respectively. Meanwhile, the energy migration from Bi3+ to Sm3+ and Tb3+ in co-doping samples was confirmed by emission/excitation spectra and luminescent decay behaviors. The mechanism of energy transfer from Bi3+ to Sm3+ has been demonstrated to be the resonant type via a dipole-dipole interaction and the critical distances between Bi3+ and Sm3+ were calculated to be 22.28 Å. Additionally, the temperature-dependent photoluminescence for as-prepared phosphors have been investigated in detail. The luminescence intensity of Sm3+ and Tb3+ ions can be sensitized to enhance by Bi3+ ion. The blue and orange-red colors can be tuned by adjusting the concentration ratio of Bi3+/Sm3+ base on the energy transfer from Bi3+ to Sm3+ ions, and the phosphors Sr2MgSi2O7:Bi3+, Tb3+ develop excellent green-emission properties, which indicate that the Sr2MgSi2O7:Bi3+, Sm3+/Tb3+ phosphors with tunable multicolor and green emissions may be of potential application in pc-white LEDs.