Optically stimulated luminescence (OSL) and thermally assisted OSL in Eu2+ – Doped BaSO4 phosphor

Abstract

BaSO4:Eu2+ phosphor has been investigated for its photoluminescence (PL), thermoluminescence (TL), TL kinetics, optically stimulated luminescence (OSL) and thermally assisted OSL (TA-OSL) response. PL spectra showed the characteristic emission of Eu2+ ion at 375 nm when excited by 320 nm. The luminescence lifetime has been measured as 40 and 628 μs of fast and slow components respectively. The TL parameters such as trap depth (E), frequency factor (s) and the order of kinetics (b) are determined. The phosphor is found to be 6 and 4 times more sensitive than CaSO4:Dy and α-Al2O3:C, respectively, in TL mode. However, its OSL sensitivity is 75% of α-Al2O3:C. It is found to possess three OSL components having photoionization cross-sections of 1.4 × 10−17, 1.2 × 10−18 and 5.2 × 10−19 cm2 respectively. The temperature dependence of OSL studies showed that integrated TA-OSL signal increases with stimulation temperature between 50 and 250 °C, while between 260 and 450 °C the signal intensity decreases. This behavior is interpreted to arise from competing effects of thermal assistance (activation energy EA = 0.063 ± 0.0012 eV) and depletion of trapped charges. This increase of OSL at elevated temperature can be employed for enhancing the sensitivity of phosphor for radiation dosimetry.