Bluish-green afterglow and blue photoluminescence of undoped BaAl(2)O(4)

Undoped BaAl(2)O(4) was derived via sol–gel combustion technique. The afterglow and photoluminescence (PL) properties of undoped BaAl(2)O(4) were explored with the combination of experiments and density functional theory (DFT) calculations. Undoped BaAl(2)O(4) is found to display bluish-green afterglow that is discernible to naked eye in dark for about 20 s. The broad afterglow spectrum of undoped BaAl(2)O(4) is peaked at around 495 nm. As a contrast, the broad PL spectrum of undoped BaAl(2)O(4) can be decomposed into a bluish-green PL band peaking at about 2.53 eV (490 nm) and a blue PL band centered at about 3.08 eV (402.6 nm). DFT calculations indicate that the defect energy levels generated by oxygen and barium vacancies are critical to the afterglow and PL of undoped BaAl(2)O(4). This work demonstrates that the oxygen and barium vacancies in undoped BaAl(2)O(4) are liable for the bluish-green afterglow and blue PL of undoped BaAl(2)O(4). The recorded bluish-green afterglow of BaAl(2)O(4) is particularly important to understand the afterglow mechanisms of rare-earth doped BaAl(2)O(4).