Effect of annealing at different time intervals on the structure, morphology and luminescent properties of MgAl₂O₄:0.3% In³⁺ nanophosphor prepared by citrate sol-gel method

Indium-doped magnesium aluminate (MgAl₂O₄:03% In³⁺) spinel powders were prepared by citrate sol-gel method. The effect of annealing period (AP) at a fixed annealing temperature (800 °C) and dopant concentration (0.3% In³⁺) on the structure, particle morphology and photoluminescent properties of the powders were investigated. The X-ray powder diffraction (XRD) results showed that the crystalline quality and crystallite sizes of the powders were influenced by the AP. Doping with 0.3% In³⁺ did not influence the major crystal structure of the MgAl₂O₄ (host) material. The scanning electron microscope (SEM) image suggested that the AP influences the particle morphology of the nanophosphor. Transmission electron microscopy (TEM) image suggested that the crystallites sizes were in the region of 10 nm. The Photoluminescence (PL) results showed that the violet emission at 388 nm and green emission at 560 nm both originated from the host material and there was no evidence of any emission from the dopant (In³⁺). Increasing the AP up to 2 h lead to luminescence enhancement, while further increase in AP lead to luminescence quenching. The Commision Internationale de l'Eclairage (CIE) co-ordinates results showed that the emission colour of all samples was in the blue region and it was not tuned by varying the AP.