Persistent luminescence of Ba2MgSi2O7:Eu2+

Ba2MgSi2O7:Eu2+,R3+ (R=Y, La–Nd, Sm–Lu) materials were prepared with a solid state reaction. The UV excited (image) and persistent luminescence bands of Ba2MgSi2O7:Eu2+ were both centered at 500 nm and thus they are due to the same Eu2+ ions. The Tm3+ co-doping induced by far the strongest enhancement of the persistent luminescence intensity and duration. The next strongest enhancement was achieved by the Er3+, Nd3+ and Pr3+ co-doping. The enhancement by the remaining R3+ co-doping ions was quite similar. The decay of the persistent luminescence consists of at least three processes. First process is very fast whereas the lifetime of the second process is in the range from 3.7 to 9 min depending on the co-doping ion. For the Pr3+, Nd3+, Er3+ and Tm3+ co-doped materials a third process with a lifetime varying from 14 to 28 min is observed. The persistent luminescence is suggested to involve lattice defects, i.e. oxygen (cation) vacancies, which create trapping levels for electrons (holes). The details of the mechanism(s) are still, however, under further investigations.