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

Thermoluminescence (TL) response of gamma-irradiated Cr3+ doped MgAl2O4 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-Mg, V-Al, Mg-Al and Al-Mg 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 Cr3+ ions with increase in Cr doping concentration. Cr3+ ions doped at octahedral sites are found to be perturbed by the presence of V-Mg, Mg-Al, Al-Mg 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 gamma-irradiation to comprehend the intertrap charge transfer among various shallow and deep trapping states.

Automated summary

The TL response of gamma-irradiated Cr3+ doped MgAl2O4 nanocrystals was studied to investigate the influence of dopant ions on intrinsic defects and trap distribution. At low doping concentration, the TL glow curve showed a dominant incomplete peak attributed to deep F+ centers and contribution from shallow trapping states. The intensity and distribution of the TL glow curve were found to be affected by an increase in Cr doping concentration, indicating the interaction between electron spins and Cr3+ ions.