White emitting GeO2-PbO-Bi2O3-SrF2 glass and nano-glass ceramics co-doped with Eu3+, Tb3+ and Tm3+ ions

The study is devoted to a luminescent glass and its devitrified counterpart (nano-glass ceramics) both triply co-doped with Eu3+, Tb3+ and Tm3+ ions. Besides for comparison glasses singly doped with Eu3+, Tb3+ or Tm3+ and a glass doubly co-doped with Eu3+ and Tb3+ were studied. The singly Tb3+ doped glass did not exhibit cross-relaxation effect. In the case of the di-doped glass energy transfers Tb3+ -> Eu3+ was certified. Then, for the tri-doped glass energy transfers Tb3+ -> Eu3+ and in reverse Eu3+ -> Tb3+ as well as Tm3+ -> Tb3+ were observed. In the emission spectrum of the triply co-doped devitrified glass, similarly as in the other Eu3+ doped glasses, band peaked at 612 nm ascribed to D-5(0) -> F-7(2) transition in Eu3+ was dominated above the D-5(0) -> F-7(2) band. It suggests that the majority of Eu3+ ( and very probably also Tb3+ and Tm3+) ions were incorporated into the residual vitreous phase of the glass-ceramics. Reduced luminescence lifetimes tau(1) of the Tb3+ and Tm3+ dopants in the triply co-doped glass in comparison to tau values of these dopants singly embedded in the glasses additionally confirms presence of the energy transfer effects in the tri-doped material. Devitrification of the tri-doped glassy phosphor did not improve its white color emission. (C) 2017 Elsevier B. V. All rights reserved.