Effect of gamma irradiation on thermoluminescence studies of LiF:Sm3+,Dy3+ nanophosphor

Nanocrystalline powders of lithium fluoride (LiF) doped with samarium (III) (Sm3+) and dysprosium (Dy3+) ions (LiF:Sm3+, Dy3+) have been synthesized through the chemical coprecipitation method at a pH value of 8. The phase purity of the asgrown samples has been confirmed by X-ray diffraction, and the average crystallite size was 32 nm, while transmission electron microscopy images showed cubical particles with size in the range 28-40 nm. Thermoluminescence (TL) studies have been carried out on samples irradiated with gamma rays using a cobalt-60 (Co-60) source in the dose range 1-50 kGy at room temperature. The effects of the concentration of dysprosium ions as a co-dopant and exposure doses on TL glow curves have been investigated. It has been found that there is a prominent TL glow peak at 411 K and a shoulder peak around 554 K at a heating rate of 5 K/s. A shift in the glow peak temperature from 400 to 411 K has also been observed in the main glow peak with increase in the irradiation dose from 1 to 50 kGy, indicating that the glow peaks follow second-order kinetics. TL kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) have also been calculated using Chen's peak-shape method.