Correlation of phase transition with the change in TL characteristics in CaSO4:Dy phosphor—effect of thermal treatment

Abstract

The study is aimed at optimising the glow curve structure of CaSO4:Dy phosphor for dosimetric purpose and also to understand the observed changes owing to thermal treatment in the thermoluminescence (TL) sensitivity and glow curve structure. The reversible changes in the intensities of the lower temperature satellite peak and the main dosimetric glow peak with temperature of thermal treatment in the temperature range 400-700 degrees C indicates the interconversion of defect complexes responsible for the glow peaks in CaSO4:Dy. Phosphor samples subjected to thermal treatment in temperature range beyond 800 degrees C, showed irreversible changes in the intensities of the lower temperature and dosimetric peaks. The changes in TL characteristics of the phosphor for thermal treatments >800 degrees C are attributed to the partial phase transition in the phosphor as confirmed by the XRD and TG/DTA analysis of the phosphor.

TL and EPR studies of CaSO4:Dy phosphor to investigate its efficacy in measurement of food irradiation dose at sub-ambient temperatures

“…In view of this, commercially available CaSO 4 :Dy (0.2 mol%) phosphor was subjected to pre-irradiation thermal treatment at 700, 800 and 900 C for a period of 2 h. As shown in Table 1, the peak height ratios (ratio of high temperature peak to low temperature peak) were observed to be decreased sharply with increasing temperature of the thermal treatment, indicating sharp rise of the low temperature peak intensity. These results were well in conformity with the reported literature (Bakshi et al, 2006). The change in glow curve structures with the annealing temperatures is shown in Fig.…”

Effect of Storage on the TL Properties of Glow Curve of Synthesis: Dy, Tm and Dy/Tm Doped CaSO4

“…4a shows the comparative TL glow curves for the three samples. It was observed that the Dy doping in CaSO 4 (i.e., CaSO 4 :Dy) exhibits two peaks at around 129°C and 208°C with main peak at 208°C while the Tm doping (CaSO 4 :Tm) showed a higher TL intensity than the Dy doping with two peaks at around 125 and 204°C, as reported elsewhere [4][5]12]. Interestingly, the co-doped sample i. CaSO 4 :Dy (0.2), Tm (0.2) resembles the TL glow curve of the Dy doped sample with no significant change in the second peak position with shift to higher temperature of first peak and with an enhanced intensity compared with CaSO 4 :Dy and CaSO 4 :Tm both, this results reading of samples stored.…”

“…It is extensively used in environmental monitoring of radiation since its qualities include a very high sensitivity, which makes it superior to many other dosimeters in this field [1,2]. Several papers have been published on the TL of [3][4][5][6][7][8][9][10][11] a single dopant RE sensitizer of either Dy or Tm and inter-comparisons of studies of different systems introduce uncertainties due to experimental errors of thermal contact, but very few have been devoted to the TL of co-doped CaSO 4 : Dy/Tm. For example CaSO 4 samples co-doped with Tm and Dy [12][13][14] show a systematic temperature difference between the dosimetric peaks of the two dopants, which cannot be explained by a simple model of isolated trapping and recombination centers.…”

Thermoluminescence, ESR and x-ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature thermal treatment

“…Post preparation annealing at a higher temperature is of particular interest in order to optimize the thermal treatment to obtain maximum TL sensitivity of this phosphor. For this purpose, we had earlier studied the TL characteristics of this phosphor subjected to post preparation annealing from 300 to 850 • C in air [8]. However, as a by-product of the earlier study it was found that an irreversible change occurs in the glow curve structure by annealing the phosphor beyond 800 • C. Lakhsmanan et al [9] have also reported similar results observed due to annealing of CaSO 4 : Dy phosphor prepared through two different routes.…”