%0 Journal Article
%T Preparation, Characterization, and Luminescence Properties of Orthorhombic Sodium Sulphate
%A Y. S. Vidya
%A B. N. Lakshminarasappa
%J Physics Research International
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/641631
%X A highly efficient thermoluminescence Na2SO4 phosphor with thenardite polymorphic structure was prepared by simple slow evaporation technique followed by subsequent calcination at 200¡ãC, 400¡ãC, and 600¡ãC 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 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 ( ), order of kinetics ( ), and frequency factor ( ) 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 ¦Ã-irradiation, suggesting that defects are unstable and decay rapidly. 1. Introduction Sulphates are attractive candidates in thermoluminescence (TL) dosimetry for the quantitative measurement of radiation dose. Due to high cost of the most popular TL dosimeters and also due to some competitions attending its reuse such as permanent radiation damage effects and the sensitivity to the annealing temperature much attention focused towards the innovation of new phosphor materials. Sodium sulphate (thenardite), though very simple in chemical composition, has been the subject of various applications. It is used for the production of glasses and paints and for thermal energy storage techniques [1, 2]. Na2SO4 exhibits a variety of phase transitions between its five anhydrous polymorphs (labelled I¨CV). The phase transformation sequence among the Na2SO4 polymorphs can be described as Na2SO4 forms two naturally occurring minerals mirabilite (Na2SO4£¿:£¿10H2O) and thenardite (Na2SO4). Both are in thermodynamic equilibrium at 32¡ãC which may be lowered to 18¡ãC in the presence of foreign ions [3]. At room temperature phase V (thenardite) is reported to be stable while phase III is metastable. Phase I, and II are high-temperature polymorphs however, phase II is reported to have a narrow stability zone. Phase IV is considered to be metastable and its phase relation and structure have yet to be well established [4¨C7]. Correcher et al. observed the spectra of
%U http://www.hindawi.com/journals/physri/2013/641631/