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ZnAl 2 O 4 nano-powders have been successfully prepared via citrate sol-gel technique. All powder samples were annealed at 600 o C for 1, 2, and 3 h. Thermogravimetric analysis (TGA) confirmed that the minimum annealing temperature of crystallization is ~ 400 °C. Fourier Transform Infrared (FTIR) results showed a series of absorption peaks in the range of 810-4000 cm-1. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) results showed that the prepared nano-crystals consists of the mixture of both cubic (ZnAl 2 O 4) and hexagonal (ZnO) structures. Ultra violet visible (UV-vis) spectroscopy revealed that the annealing time (AT) influences the band gap of the prepared phosphor materials. When the 2 samples were excited at 275 nm, two emission peaks at 428 nm (violet) and 561 nm (green-yellow) were observed and they are attributed to the defects levels within the ZnO and ZnAl 2 O 4 band gaps. The Commission Internationale de l'Elcairage (CIE) colour coordinates confirmed that all the prepared samples exhibit the violet emission and varying the AT does not influence the emission colour.

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