Emission properties of Sn²⁺ and Sm³⁺ Co-doped barium phosphate glass

Co-doping of a P₂O₅:BaO glass matrix with divalent tin and trivalent samarium ions has been realized by the melt-quenching technique with the purpose of investigating the material's luminescent properties. Photoluminescence excitation spectra obtained by monitoring Sm ^{3+ 4}G_5/2 emission showed a broad excitation band around 290 nm (absent in a Sm³⁺-doped reference), typical of donor/acceptor energy transfer. Under such excitation, the material exhibits a reddish-white emission. Time-resolved spectra recorded under the 290-nm excitation (non-resonant with Sm³⁺ excitation peaks) exposed a broad blue-white band characteristic of twofold-coordinated Sn centers and orange-red emission bands of Sm³⁺ ions, which appeared well separated in time in accord with their emission decay dynamics. Consequently, the data indicate that light absorption occurs at Sn centers (donors) followed by energy transfer to samarium ions (acceptors) which results in populating the ⁴G_5/2 emitting state in Sm³⁺. Energy transfer pathways likely resulting in the sensitization of Sm³⁺ photoluminescence are discussed. Results are put into context in terms of the potential of SnO and rare-earth co-doped barium phosphate glasses for use in white light-emitting devices.