Synthesis, Characterization and Thermoluminescence Studies of LiNaSO4: Eu3+ nanophosphor

Abstract

Na2SO4, LiNaSO4 and LiNaSO4: Eu 3+ nanophosphors were successfully synthesized by slow evaporation technique followed by calcination at 400° C. The resultant products were characterized by using powder Xray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV -Vis, scanning electron microscope (SEM) and transmission electron microscope (TEM). Doping with Li + ion stabilized the thenardite phase (Phase V) while, codoping with Eu 3+ promoted the phase transformation from stable thenardite to metastable mirabilite (Phase III) crystal structure. The average crystallite size was calculated by using Debye -Scherrer's formula and Williamson -Hall (W -H) plots. The optical energy band gap (Eg) of Na2SO4, LiNaSO4 and LiNaSO4: Eu 3+ were estimated from Wood and Tauc's relation which varies from 4.2 -4.33 eV. Thermoluminescence (TL) studies were investigated by using γ -irradiation in the dose range 0.5 -5 kGy at a heating rate of 5 °C s -1 . A well resolved glow peaks at ~ 180 °C, ~ 150 °C and ~115 °C were recorded for Na2SO4, LiNaSO4 and LiNaSO4: Eu 3+ nanophosphors respectively. It was observed that isovalent doping of Li + served as quencher, while codoping of hypervalent Eu 3+ acted as activator to enhance the TL intensity of glow peak. In the present study, the extent of TL fading of LiNaSO4: Eu 3+ was 31 % compared to LiNaSO4 (52 %) and Na2SO4 (59 %). So, LiNaSO4: Eu 3+ phosphor might also have potential use in dosimetry. The kinetic parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) was estimated and the results were discussed.