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 as-grown 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 (60Co) 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.