Effects of distorted lattice and nonequal-valvence substitution on the long lasting phosphorescence of Eu2+ and Gd3+ doped RMg2(PO4)2 (R=Sr, Ba) phosphors

The afterglow of Eu(2+) activated SrMg(2)(PO(4))(2) can be greatly enhanced by the codoping of Gd(3+), as well as an interesting phenomenon of the improvement of the efficiency of the excitation light. However, Eu(2+) activated BaMg(2)(PO(4))(2) does not show the phosphorescence until the codoping of Gd(3+). It is suggested that the codoping of Gd(3+) improve the electron storage ability of material by acting as electron-trapping centers resulted from the nonequal-valence substitution of Gd(3+) replacing Sr(2+) and Ba(3+). And the Gd(3+)-induced enhancement of the excitation efficiency of Eu and Gd codoped SrMg(2)(PO(4))(2) is due to the improvement of the energy transfer efficiency caused by the distortion of lattice of Gd(3+) located at the sites of Sr(2+). (C) 2010 American Institute of Physics. [doi:10.1063/1.3475989]