Influence of Li+ and Dy3+ on structural and thermoluminescence studies of sodium sulfate

Abstract

Na2SO4, Na2SO4: Dy3+, LiNaSO4 and LiNaSO4: Dy3+ nanoparticles successfully synthesized by slow evaporation technique followed by calcination at 400 oC. The resultant products were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and UV–Vis spectroscopy. The average crystallite size was calculated using Debye–Scherrer’s formula and Williamson–Hall’s (W–H) plots. The optical energy band gap (E g) was estimated from Wood and Tauc’s relation, which varies from 3.70 to 4.45 eV. The variation in band gap values attributed to large degree of structural defects. Thermoluminescence studies were investigated using γ-irradiation in the dose range 0.5–5 kGy at a heating rate of 5 K s−1. The samples Na2SO4 and LiNaSO4 showed a well-resolved glow peak at ~180 and ~170 °C, respectively. The prominent glow peak at ~175 °C along with shouldered peak at ~60 °C was observed for Na2SO4: Dy3+. LiNaSO4: Dy3+ showed prominent glow peak at ~100 °C and a small shoulder peak at ~180 °C. The addition of isovalent (Li+) quenches the TL intensity, whereas the hypervalent (Dy3+) increases the intensity of Na2SO4. The variations of TL intensity for all the phosphors follow linear behavior up to 5 kGy and were useful in radiation dosimetry. The kinetic parameters (E, b and s) were estimated from the glow peak shape method.