Preparation, characterization, and luminescence properties of orthorhombic sodium sulphate

Abstract

A highly efficient thermoluminescence Na2SO4 phosphor with thenardite polymorphic structure was prepared by simple slow evaporation technique followed by subsequent calcination at 200°C, 400°C, and 600°C for 4 h and the resultant crystals were characterized by various analytical techniques. All the samples exhibited thermodynamically stable thenardite phase and the grain growth was increased for the calcined samples. SEM analysis indicated the fine distribution of twinned orthogonal prism and pyramidal structure without any agglomeration. The electron spin resonance spectroscopy showed the existence of S O 4 - radicals as trap centre. The thermoluminescence behavior suggested the charge carrier recombination dynamics in the thenardite sample followed second-order kinetics. The trapping parameters such as activation energy (E), order of kinetics (b), and frequency factor (s) have been determined using Chen's peak shape method. Further fading of the TL intensity of Na2SO4 showed that thenardite is quite suitable for radiation dosimetry even up to 15 days. The photoluminescence band of Na2SO4 reduced in its intensity after γ-irradiation, suggesting that defects are unstable and decay rapidly. © 2013 Y. S. Vidya and B. N. Lakshminarasappa.