Investigation of energy absorption and transfer process of Tb3+ or Eu3+ excited Na3Gd(PO4)2 in the VUV region

Na3Gd(PO4)2, Na3Gd0.94(PO4)2:0.06Tb3+ and Na3Gd0.94(PO4)2:0.06Eu3+ are prepared by solid-state reaction and their photoluminescence (PL) properties are investigated in the ultraviolet (UV) and vacuum ultraviolet (VUV) region. The obtained results show that Na3Gd0.94(PO4)2:0.06Tb3+ has an efficient emission under 147 nm excitation, but the emission efficiency of Na3Gd0.94(PO4)2:0.06Eu3+ is low under 147 nm excitation. We discuss the energy absorption and transfer process in the VUV region to solve the special phenomenon.