MgAl2O4 spinel: Synthesis, carbon incorporation and defect-induced luminescence

• Synthesis of MgAl2O4.
• Carbon incorporation in spinel lattice.
• Defect induced emission.
• Identification of defects.
• Blue emission from Carbon doped sample.

The present work explores the synthesis of carbon-doped MgAl2O4 and investigates the effect of doping on the photophysical properties of MgAl2O4. Pure MgAl2O4 spinel was synthesized by gel combustion followed by annealing at 1100 °C. The carbon doping was performed by two methods. The first method involved heating the sample with electron beam (from electron gun) in graphite crucible (A) and second method involved heating the sample up to 2100 °C in graphite furnace (B). The photoluminescence spectroscopy exhibited defect-induced emissions with enhanced intensity in the case of sample B. A significant blue shift in the emission band was also observed in the case of sample B. The photoluminescence decay studies indicated that multiple trapping and detrapping events are experienced before the radiative recombination process, which eventually occurs. Average lifetime was observed to be 4.83 μs which is typical of defect-related emission. The results were complimented by electron paramagnetic resonance (EPR) technique. The CIE co-ordinates for sample B were found to be x = 0.231 and y = 0.227 which establish it as a blue-emitter.