Energy Transfer between Gd 3+ and Other Rare-earth Ions in GdPO 4 under Vacuum UV Excitation

Under 172 nm light excitation, energy transfer from Pr 3+ , Nd 3+ , Tb 3+ or Tm 3+ to Gd 3+ resulting in strong Gd 3+ emission at 312 nm was observed in GdPO 4 doped with one of these ions. Among them, Pr 3+ provides the strongest Gd 3+ emission and Tm 3+ is the second best. A wide energy gap between the 5d state and 4f levels of Pr 3+ resulting from a simple electron configuration of 4f 2 leads to energy transfer from a 5d-to-4f transition of Pr 3+ to a 4f-to-4f absorption of Gd 3+ . Presumably, this is also the case with Tm 3+ , which has an electron configuration similar to that of Pr 3+ . The quantum output of the Gd 3+ emission from GdPO 4 :Pr 3+ (1 mol.%) relative to the blue luminescence of BaMgAl 10 O 17 :Eu 2+ , a commercial phosphor for plasma display panels, is about 37% under 172 nm excitation. Reverse energy transfer from Gd 3+ to Dy 3+ occurs under excitation by the Gd 3+ absorption at 276 nm.