Mechano and Thermoluminescence of Gamma-irradiated CaSO4:Dy Phosphor

Abstract

In order to have a better idea of the interaction of the defect centres produced by y-irradiation with dislocation in the processes of deformation destruction, mechanoluminescence (ML) and thermoluminescence (TL) of gamma-irradiated CaSO4:Dy, these phosphors have been investigated. CaSO4:Dy phosphors were prepared by dissolving CaSO4.2H2O in sulphuric acid and evaporating the excess acid around 300 degrees C. ML was excited impulsively by dropping a load on to the sample. Two peaks have been observed in the ML intensity against time curve. The total light output, i.e. integrated ML intensity, increases with concentration of dopant, strain rate and with irradiation doses. The TL glow curves of CaSO4:Dy phosphors at different concentrations of dopant and irradiation doses were also recorded. Studies of the influence of post-irradiation annealing on the ML of CaSO4:Dy show that with the removal of the TL dosemetric peak (approximately 210 degrees C) the ML intensity decreases markedly. A spectroscopic study of ML and TL has also been carried out to elucidate the mechanism of ML. Correlation between ML and TL has also been found.

Impulsive excitation of mechanoluminescence in gamma-irradiated CaSO4:Eu phosphors

“…On the basis of ESR and step annealing measurements, Nair et al (13) have concluded that the TL peak (∼110 • C) is closely related to SO − 4 defect centres. In the TL glow curves of CaSO 4 :Dy phosphors, only one peak is observed at around 220 • C and two peaks close to each other are observed in the ML intensity against time curve (7). In the TL glow curves of CaSO 4 :Eu phosphors, in addition to a dosimetric peak at 210 • C, another sharp and sensitive TL peak occurs at 110 • C. Hence, we expect that the defect centres corresponding to the 110 • C TL peak play an important role in the ML excitation process.…”

“…In most of the materials, only one peak is observed in the ML intensity against time curve, and the ML emission stops as soon as the deformation is interrupted (11). In the ML glow curve of CaSO 4 :Dy phosphors, two peaks close to each other are observed (7), and it is believed that the fist peak is attributed to the ML produced due to charging of the newly created surface and the second peak is due to the release of carriers from the shallow traps, which takes place later on due to the thermal vibration of the lattice. The occurrence of the second and third peaks in the ML glow curve of CaSO 4 :Eu phosphors indicates that some of the carriers excited by mechanical action have transferred to two types of shallow traps, having different traps depth.…”

“…The ML of X-or γ -irradiated alkali halides has been the most extensively studied in the past two decades and the correlation between ML and thermoluminescence (TL) has been confirmed. We have also studied the ML and TL of CaSO 4 :Dy and (K 2 Mg 2 :Dy)(SO 4 ) 3 phosphors (7,8). It is suggested that the recombination of electrons with free radicals (anion radicals produced by gamma irradiation) released from the traps during thermal or mechanical excitation is responsible for luminescence in this system.…”

Mechanoluminescence characterizations in γ-irradiated and Dy3+ activated (K0.5Na0.5)Cl phosphor for accidental radiation dosimetry

“…Meyer and Winnacker [12] have reported the ML and thermoluminescence in c-irradiated KCl crystals. The ML intensity of coloured alkali halide crystals and CaSO 4 :Dy phosphor increases with gamma rays dose given to them [13][14][15].…”

Aplicação e avanços da espectroscopia de luminescência em análises farmacêuticas

“…11 Contudo, cabe ressaltar que ainda existem a sonoluminescência, [25][26][27][28] a mecano-ou tribulominescência, [29][30][31][32][33][34] a radioluminescência, [35][36][37][38] a termoluminescência, 34,39,40 a bioluminescência, 41 entre outros. Nesta revisão, serão abordados trabalhos envolvendo a determinação de fármacos baseados em fenômenos fotoluminescentes e quimiluminescentes.…”