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

Abstract

Thermoluminescence (TL), electron spin resonance (ESR) and x ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature treatment were carried out. Analysis of the TL glow curve indicated that the dosimetric glow peak at 240 °C reduces, whereas the low temperature satellite peak increases with the increase in the annealing temperature in the range 650–1000 °C. The influence of the annealing atmosphere on the TL glow curve structure was also observed. Reduction of the photoluminescence intensity of the annealed phosphor indicated that the environment of Dy3+ ions might have undergone some change due to high temperature treatment. Reduction in the ESR signal intensity corresponding to and radicals was observed initially with the increase in the annealing temperaure; subsequently their intensity increased with temperature. Signals due to the radical vanished, when the phosphor was annealed beyond 800 °C. A signal corresponding to SH2− radicals was also observed in the ESR spectra for samples subjected to annealing in the temperature regime 800–1000 °C. XRD of the in situ annealed phosphor showed a change in the unit cell parameters. An endothermic peak at 860 °C in the DTA spectrum was observed.

Thermoluminescence, photoluminescence and optically stimulated luminescence characteristics of CaSO4:Eu phosphor: Experimental and density functional theory (DFT) investigations

“…These results are also similar to the results already available in the literature[46,53]. As reported earlier[28,45,54], in CaSO4:Eu, Eu exists in the divalent as well as the trivalent state in the CaSO4 lattice and emits fluorescence on both the valency states. The redox reactions in Eu doped CaSO4 phosphor, i.e., conversion of Eu 3+ E 2+ on annealing as well as on irradiation are well known[53].…”

“…The changes in glow curve structures could also take place, however, it is not found that prominent as could be seen from TL glow curves of CaSO4:Eu@600 and CaSO4:Eu@900 samples (if we think that the particles have grown much bigger on annealing at 900 o C than at 600 o C for 2 h). The environment of the luminescent centers and hence glow curve structure could be affected by diffusion of atmospheric oxygen during annealing at much higher temperatures [45]. with respect to the annealing temperature is shown in Fig.…”

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

“…These lines were attributed to and SO 3 À , SO 4 À and O 3 À radicals respectively. The g values obtained are compared well with those reported in the literature (Mauricio et al, 1996;Sharaf and Hassan, 2004;Gupta et al, 1974;Natarajan et al, 1988;Seshagiri et al, 1988;Bakshi et al, 2008). From Figs.…”

“…Ltd. Hyderabad, India) with a linear heating rate of 2 C per second from room temperature to 300 C. Neutral density filters (Melles Griot BV, Netherlands) of optical densities 3.0 and transmittance 0.01% were used to avoid saturation of Photo Multiplier Tube (PMT). The peak height is vertical length of the peak tip from the temperature axis measured directly from the glow curve (Bakshi et al, 2008;Mathur et al, 1999). Control and irradiated phosphors were stored in dark place at normal laboratory condition when they were not in use.…”

Thermoluminescence dose–response of synthesized and doped hydroxyapatite: effect of formed crystal phases

“…As any change in the structure of the material can lead to a change in the dosimetry properties, it is essential to study the phase structure from a practical point of view. [11,39,[47][48][49][50][51][52][53] The crystal structure of hydroxyapatite has been studied in several papers, [52,54,55] but its effect on the TL properties of HAP has not yet been investigated. Therefore, in this research work, the aim is to investigate the effect of the crystal structure of HAP on its TL response, using two different synthesis methods, hydrolysis and hydrothermal methods, the effect of annealing temperature, addition of dopants, and other dosimetry behaviour of this substance.…”