Luminescence Dynamics of BaAl₂O₄:Eu²⁺ Phosphor

We studied steady-state and time-resolved photoluminescence of Eu doped BaAl₂O₄ phosphor. The undoped BaAl₂O₄ sample shows a dominant blue emission band at ~ 428 nm and two secondary maxima at ~ 405 and 456 nm due to F-centre and aggregate defects such as F₂ -centre. The samples after doping of Eu at 1-5% show additional emission bands at ~ 485 and 518 nm due to Eu²⁺ centre and a red emission band at ~ 657 nm is attributed to Eu³⁺ centre. The sample doped with 2% of Eu shows anomalous emission having the dominant peak at ~ 494 nm. The average luminescence lifetime of the emission band at ~ 428 nm in the undoped sample was estimated to be (3.29 ± 0.91) ns. The average luminescence lifetime of this emission band after doping of Eu was found to increase by 10² orders of magnitude. The intensity of the 428 nm blue emission band was found to quench after doping of Eu beyond 3%. The concentration quenching effect was attributed to dipole-quadrupole interaction. Further, a non-radiative fluorescence energy transfer mechanism from an extrinsic Eu²⁺ centre to an intrinsic F-centre is proposed to describe the luminescence dynamics of the samples.