Trapping processes of 5d electrons in Ce³⁺ doped SrAl₂O₄

Ce³⁺-doped SrAl₂O₄ single-crystal fibers have been prepared by laser-heated pedestal growth method. A broad emission band peaking at 385 nm and originating from the Ce³⁺ 5d-4f transition is observed with excitations at 340, 320, 291, and 259 nm, which correspond to the crystal field splitting components of the Ce³⁺ 5d states in SrAl₂O₄. The emission shows strong persistence for longer than 10 h after UV radiation at 254 nm from mercury lamp. Trapping dynamics of 5d electrons of Ce³⁺ in SrAl₂O₄ host is studied. The electron traps at 0.75 eV are found to be responsible for the long persistent phosphorescence. Excitation-dependent thermoluminescence spectra are also recorded and analyzed. The lowest 5d state of Ce³⁺ in SrAl₂O₄ is found to be about 0.1 eV below the host conduction band.