Synthesis and photoluminescence properties of red-emitting NaLaMgWO6:Sm3+,Eu3+ phosphors for white LED applications

Abstract

A series of red-emitting NaLaMgWO6:Sm3+,Eu3+ phosphors were successfully synthesized by the solid-state reaction method. The crystal structure, morphology and photoluminescence properties were investigated in detail. The NaLaMgWO6 compound has monoclinic structure with the space group C2/m. Upon excitation of the near-ultraviolet light, the Sm3+ singly doped and Eu3+singly doped phosphors exhibit red emission at 600 nm (4G5/2→6H7/2 transition of Sm3+) and 617 nm (5D0→7F2 transition of Eu3+), respectively, while the Sm3+, Eu3+ co-doped phosphors show the characteristic transition of Eu3+ whether excited by 397 or 406 nm. This indicates the existence of the energy transfer from Sm3+ to Eu3+ ions. Furthermore, the mechanism of energy transfer and energy transfer efficiency were confirmed by the decay time of Sm3+ ion in NaLaMgWO6:Sm3+,Eu3+ phosphors. The mechanism of energy transfer between Sm3+ and Eu3+ is proved to be dipole-dipole interaction, and the energy transfer efficiency of NaLa0.65MgWO6:0.05Sm3+,0.3Eu3+ phosphor is calculated to be 38.89%. The temperature dependent emission spectra demonstrate that the NaLaMgWO6:Sm3+,Eu3+ phosphor has a good thermal stability with an thermal activation energy ΔE of 0.241 eV. The CIE chromaticity coordinate is calculated to be (x = 0.661, y = 0.339).