Synthesis and characterization of ultraviolet-emitting cerium-ion-doped SrBPO5 phosphors

The synthesis and characteristics of strontium borate phosphate phosphors doped with cerium ions were investigated in this study. The synthesis of Sr0.95Ce0.05BPO5 in oxidizing atmosphere results in partial conversion of Ce4+ ions into Ce3+ ions. The luminescent characteristics reveal that Ce3+ ions occupy two principal sites in the host. The dominant emission at 317 nm on 275-nm excitation is attributed to Ce3+ ions located at Sr2+ sites without local charge compensation. The weak emission at 330 nm due to 295-nm excitation is ascribed to Ce3+ ions located at Sr2+ sites in association with charge compensatory vacancy. The reduction of Ce4+ ions to Ce3+ ions occurs in Sr0.95Ce0.05BPO5 heated in the reducing atmosphere. For Sr0.9Ce0.05Na0.05BPO5 and Sr0.9Ce0.05Li0.05BPO5 phosphors, enhancement in luminescence is observed due to the codoping of monovalent ions. The increased luminescence of these phosphors is attributed to the decrease in non-radiative energy transfer.