Cr dopant induced tailoring of intrinsic defects and trap distribution in MgAl2O4 nanocrystals: electron spin resonance and thermoluminescence

Abstract Thermoluminescence (TL) response of γ -irradiated Cr 3+ doped MgAl 2 O 4 nanocrystals is studied to investigate the impact of dopant ions on intrinsic defects and trap distribution. At low doping concentration, the broad TL glow curve has a dominant incomplete peak attributed to deep F + centers around 673 K and contribution from shallow V M g , V A l , M g A l and A l M g trapping states in low temperature region. TL glow curve intensity and trap distribution is found to be influenced with increase in Cr doping concentration. Electron spin resonance spectra show the interaction of electron spins at paramagnetic F + /V − centers with isolated and paired Cr 3+ ions with increase in Cr doping concentration. Cr 3+ ions doped at octahedral sites are found to be perturbed by the presence of V M g , M g A l , A l M g etc defect centers and may cause the formation of Cr associated defect clusters at higher doping concentration. A trapping mechanism is proposed as per the TL response obtained upon γ -irradiation to comprehend the intertrap charge transfer among various shallow and deep trapping states.