Radiative Properties of the Blue BaAl[sub 2]S[sub 4]:Eu[sup 2+] Phosphor

Abstract

The optical properties of BaAl2S4BaAl2S4 doped with Eu2+Eu2+ were investigated. The synthesis was performed in evacuated and sealed quartz ampul at 1000°C during 1 h, then at 840°C during 20 h. With absorption, excitation, and emission spectra we have determined the crystal-field splitting, the redshift, the influence of the lattice vibration properties, and the thermal quenching of the luminescence. The crystal-field splitting of Eu2+Eu2+ in BaAl2S4BaAl2S4 was estimated on the order of 8000 to 10000cm−110000cm−1 and the Huang-Rhys parameter S=5±1S=5±1 corresponds to an intermediate electron-phonon coupling regime. The mean phonon energy for BaAl2S4BaAl2S4 was evaluated by optical and Raman methods, and the obtained values were 32±532±5 and 40 meV, respectively. These results confirm the very interesting properties of this blue BaAl2S4:Eu2+BaAl2S4:Eu2+ phosphor, the most important being the very slight thermal quenching of the luminescence.