Luminescence dynamics of MgGa₂O₄ prepared by solution combustion synthesis

Magnesium gallate (MgGa₂O₄) was synthesized by solution combustion synthesis method at 500 °C. The X-ray diffraction (XRD) pattern indicates that the prepared compound crystalized into a single phase, and a porous morphology associated with combustion was observed from the image of the scanning electron microscopy (SEM). A diffuse reflectance spectrum was recorded using the UV–Vis–NIR absorption spectrometer, which revealed the band-to-band absorption edge, from which the band gap of the material was approximated using the Kubelka-Munk relation. The photoluminescence (PL) emission displayed a broad blue emission from 350 to 600 nm, when the sample was excited with a 235 nm beam. The thermoluminescence (TL) spectroscopy was used to prove that the associated kinetics in trapping and de-trapping of electrons by the electron trapping centres were of general order. The corresponding depths of the dominant electron trapping centres were approximated to 0.65 ± 0.01eV to 1.23 ± 0.01eV. Using the general gradient approximation (GGA-DFT) as implemented within the CASTEP code, we found that the MgGa₂O₄ compound has energy levels close to the conduction band, attributed to oxygen vacancies.