Effects of annealing period on the structure and photoluminescence of the mixed phases ZnAl2O4 /ZnO/SrAl2O4/Sr3Al2O6:0.025% Tb3+ nanophosphor synthesized by sol-gel technique

Abstract Nanophosphor powders of the mixed phases of ZnAl 2 O 4 /ZnO/SrAl 2 O 4 /Sr 3 Al 2 O 6 (ZZSS) doped with Tb 3+ (ZZSS:0.025%Tb 3+ ) were successfully prepared by sol-gel technique. The effect of the annealing period at a fixed annealing temperature (1000 °C) and dopant concentration (0.025% Tb 3+ ) on the structure and photoluminescence properties was investigated. X-ray diffraction results revealed that the crystallite size was influenced by the annealing period. Scanning electron microscopy showed that varying the annealing period influenced the particle morphology of the prepared nanophosphor material. High resolution transmission electron microscopy confirmed that the prepared material is on the nanoscale. The photoluminescence results showed that the ZZSS emits at 585 nm when excited at 374 nm, which is attributed to the defects centres within the ZnO phase. The Tb 3+ doped samples showed emissions peaks at 545, 590 and 623 nm which were attributed to the 4f transitions of Tb 3+ , specifically 5 D 4 → 7 F J (J = 5, 4, 3). Increasing the annealing period up to 5.4 h led to luminescence enhancements, while a further increase led to quenching. The Commision Internationale de l’Eclairage coordinates showed that the greenish emission colour could be tuned by varying the annealing period.