Energy transfer and luminescent properties of Pr3+ and/or Dy3+ doped NaYF4 and NaGdF4

The phosphors that are able to convert vacuum ultraviolet (VUV) light into visible light are demanded for the development of novel displaying and lighting devices. NaYF4:Pr3+,Dy3+, NaGdF4:Pr3+, NaGdF4:Dy3+ and NaGdF4:Pr3+,Dy3+ were prepared by hydrothermal synthesis method and their luminescent properties in VUV-vis spectral region were investigated at room temperature. For NaYF4:Pr3+,Dy3+, no energy transfer process from Pr3+ to Dy3+ was observed. However, the introduction of Gd3+ into the fluoride lattice led to intense Dy3+ emissions upon Pr3+ 4f5d state excitation. Gd3+ acted as an intermediate, resulting in efficient energy transfer from Pr3+ to Dy3+ in NaGdF4. Pr3+ transferred most of its energy to Gd3+, and then the energy was transferred from Gd3+ to Dy3+. So NaGdF4:Pr3+,Dy3+ not only took full advantage of the intense Pr3+ 4f5d absorption, but converted the VUV excitation light into the near-white emission of Dy3+.