Luminescence properties and energy transfers of NaLa(WO4)2:Sm3+:Ce3+ phosphor

A series of NaLa(WO4)2:Sm3+:Ce3+ phosphors are prepared by the hydrothermal method. The structure, morphology, luminescent properties of sample are characterized with X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and fluorescence spectrophotometer. The results show that all the obtained products have the scheelite structure with ellipsoidal shapes. Ce3+ has quenching effects on luminescence properties of NaLa(WO4)2:Sm3+ phosphors at high Ce3+ doping concentration. When the Ce3+ molar content is 1%, the intensity of the excitation and emission spectra is the maximum. It indicates that when the sensitizer Ce3+ has the molar content of 1%, the sensitizing ability of luminescent properties of NaLa(WO4)2:Sm3+:Ce3+ phosphors is the strongest. That is, Ce3+ can transfer energy to Sm3+. The critical distance of Ce3+ → Sm3+ energy transfer is 2.196 nm. The type of energy transfer of Ce3+ → Sm3+ is electric multi-pole interaction. The maximum energy transfer efficiency of Ce3+ → Sm3+ in NaLa(WO4)2:Sm3+:Ce3+ phosphors can reach 15.17%. The temperature-dependent emission spectra demonstrates that the NaLa(WO4)2: 0.02Sm3+:0.01Ce3+ phosphor has a good thermal stability with a thermal activation energy ΔE of 0.2789 eV. The CIE coordinates show that the phosphor is red, and is the potential red phosphor for LEDs.