Energy trapping to substitutional and charge compensation defects in persistent luminescent BaAl₂O₄:Tb³⁺

Abstract The holistic approach of the photoluminescence (PL), thermoluminescence (TL), and persistent luminescence properties at room temperature of BaAl 2 O 4 :Tb 3+ were investigated in detail using a wide range of techniques. Materials were obtained using a solution combustion synthesis. The x-ray powder diffraction patterns of nondoped and Tb 3+ doped BaAl 2 O 4 indicated the hexagonal phase, and a Tb 4 O 7 solid solution was observed at 4 and 5 mol% Tb doped aluminate. X-ray photoelectron spectroscopy revealed that Ba occupied one site and that Tb ions occupied this site as Tb 3+ as well as Tb IV . PL emission in blue, green, and red was observed under an excitation at 228 nm, that originated from the interconfigurational 4f 8 –4f 7 5d 1 transitions of Tb 3+ . Time-of-flight secondary ion mass spectroscopy, UV–vis diffuse reflectance, and PL revealed the presence of a Cr 3+ impurity. The 0.5 mol% Tb 3+ doped BaAl 2 O 4 exhibited a strong TL band at 354, 437 and 598 K, which were attributed to the traps formed by Tb 3+ doping and subsequent O 2− charge compensation. A persistent luminescence mechanism was constructed for the Tb 3+ doped BaAl 2 O 4 . After the energy was stored in thermally liberated Tb 3+ in the Ba 2+ substitution sites and charge compensation defects, the Tb 3+ was the source of the continuous luminescence.