Effect of M3+ (M = Bi, Al) co-doping on the luminescence enhancement of Ca2ZnSi2O7:Sm3+ orange-red−emitting phosphors

In this paper, the luminescence properties of Ca2ZnSi2O7:Sm3+ phosphors were improved by co-doping with M3+ (M = Bi, Al) via the sol-combustion method. The structure and luminescence properties of the Ca2ZnSi2O7:Sm3+, M3+ samples were investigated in detail, especially the luminescence enhancement effect of Bi3+/Al3+ co-doping. XRD results indicated that moderate Bi3+/Al3+ co-doping in the host structure did not change the tetragonal structure of Ca2ZnSi2O7. The series of Ca2ZnSi2O7:Sm3+, M3+ phosphors could be excited by 402 nm near-ultraviolet light and several significant emission peaks were obtained at 567, 604 and 650 nm, which originated from the electron transitions of Sm3+ from 4G5/2 to 6H5/2, 6H7/2 and 6H9/2 levels, respectively. The luminescence intensity of Ca2ZnSi2O7:Sm3+ was markedly enhanced through Bi3+/Al3+ co-doping, which could be explained by Al3+ decreasing the crystal field symmetry and greatly increasing the red luminescence intensity, and Bi3+ functioning as a sensitizer to increasing the luminescence intensity through energy transfer from Bi3+ to Sm3+ ions. In conclusion, the excellent Ca2ZnSi2O7:Sm3+, M3+ phosphors have potential application as red phosphors in white light emitting diodes.