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 Sr_0.95Ce_0.05BPO₅ 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 Sr_0.95Ce_0.05BPO₅ heated in the reducing atmosphere. For Sr_0.9Ce_0.05Na_0.05BPO₅ and Sr_0.9Ce_0.05Li_0.05BPO₅ 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.