Thermally stimulated processes involving defects in γ- and x-irradiated spinel (MgAl2O4)

Thermally stimulated conductivity (TSC) and thermally stimulated luminescence (TSL) of spinel single crystals exposed to ionizing radiation have been studied. TSC exhibits peaks at 70, 125, and 340 °C whereas TSL peaks occur at 70 and 260 °C. The 70 °C peak has an activation energy of 0.95 eV and is due to electron release; it has two main spectral components at 260 nm (4.8 eV) and 310 nm (4.0 eV) due to electron capture at trapped holes. The 260 °C TSL peak is broad but singly activated (1.5 eV activation) and is dominated by 710 nm (1.75 eV) and 520 nm (2.39 eV) emission due to hole capture at Cr2+ and V2+, respectively. The broad 340° TSC peak appears to contain a substantial contribution due to electron release in the 240–310 °C range which makes only a small contribution (260 and 310-nm light) to the TSL peak in this region. Dose dependence and room-temperature decay indicate that initially a substantial portion of the 260-nm afterglow is due to tunneling recombination.