K3Na(SO4)2 : Eu nanocrystalline powder was synthesized by the chemical co-precipitation method. The x-ray diffraction pattern of the nanomaterials shows a hexagonal structure for its crystals having grain size of ∼28 nm. Transmission electron microscopy revealed that the K3Na(SO4)2 : Eu nanoparticles are single crystals with almost a uniform shape and size. Thermoluminescence (TL) was taken after irradiating the samples at various exposures of γ-rays from a 60Co source. A prominent TL glow peak is observed at 423 K along with three small peaks/shoulders at around 382, 460 and 509 K. The observed TL sensitivity of the prepared nanocrystalline powder is around 4 times more than that of LiF : Mg,Ti (TLD-100) phosphor. The 423 K peak of the nanomaterial phosphor eventually shows a near linear response with exposures increasing up to very high values (as high as 70 kGy), where all the other TLD phosphors saturate. This property along with its other desired properties such as high sensitivity, relatively simple glow curve structure and low fading makes the nanocrystalline phosphor a suitable dosimeter to estimate low as well as high exposures of γ-rays. TL analysis using the glow curve deconvolution technique was also done for determining different trapping parameters.
Nanocrystalline Ba0.97Ca0.03SO4 : Eu having a grain size of 58 nm has been prepared and a comparative study has been done with its corresponding microcrystalline form. The thermoluminescence (TL) glow curve of the nanophosphor has a prominent peak at 161 °C and a very small hump at 225 °C. The TL sensitivity of the nanophosphor is about 0.1 times that of the microphosphor. Kinetics parameters of the TL peaks of the nanophosphor are obtained and are compared with those of the microphosphor. The TL response of the nanophosphor is linear in the dose range 1 Gy–20 KGy, which is much wider than that of its corresponding microcrystalline form. The glow curve shape and structure also do not change in the linear dose range and, since the TL response is linear at higher doses, the nanophosphor is quite well suited for high dose measurements. Photoluminescence emission spectra of the nano- and the microphosphors are also studied and their results correlated with other experimental findings.
Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low‐Zeff, tissue‐equivalent material that is commonly used for medical dosimetry of ionizing radiations such as gamma and X‐rays using the thermoluminescence (TL) technique. Nanocrystals of the same material are produced and their TL characteristics are studied. It is found that the nanocrystalline MgB4O7:Dy with a dopant concentration of 1000 ppm is the most sensitive amongst varying dopant concentrations, with its sensitivity equal to 0.025 times that of the standard phosphor CaSO4:Dy. The glow curve has two peaks at 154 °C and 221 °C. The nanophosphor has very poor sensitivity for low doses up to 10 Gy but beyond this dose the phosphor exhibits a linear response up to 5000 Gy. On increasing the dose further the response first becomes supralinear and then sublinear, finally resulting into saturation. Considering also its low fading particularly under post‐irradiation annealing and excellent reusability features, this nanophosphor may be used for high dose (10–5000 Gy) measurements of ionizing radiations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effects of irradiation by 48 MeV Li3+ and 150 MeV Ag12+ ion beams on the thermoluminescence (TL) of BaSO4 : Eu phosphor are studied. Samples in the form of pellets were exposed to different fluences in the range 1 × 109–5 × 1011 ions cm−2. The modifications in TL glow curves of the materials irradiated by lithium (Li) and silver (Ag) beams are essentially similar to those induced by γ-ray irradiation. There is a significant variation in the relative intensity between the main glow peak at 497 K and the small shoulder at 465 K. This variation is more dominant in the samples irradiated by Ag ions. This has been attributed to the change in the population of the luminescent/trapping centres (LCs/TCs) during the bombardment by high-energy heavy ions. The relative TL efficiency values of BaSO4 : Eu to 48 MeV Li and 150 MeV Ag ion beams have been measured relative to 0.662 MeV γ-rays of 137Cs and are found to be 0.374 and 0.0017, respectively. It is found that BaSO4 : Eu phosphor is suitable for recording irradiation from light ions (Li) as well as heavy ions (Ag) as it shows linearity in its TL responses over wide ranges of fluences of ion beams. It is linear in the ranges 1 × 109–1 × 1011 and 1 × 109–1 × 1010 ions cm−2 for Li and Ag ion beams, respectively. This property along with its low fading make BaSO4 : Eu phosphor a good candidate to be used as a dosimeter for cosmic rays and medical applications.
The modification of thermoluminescence (TL) and photoluminescence (PL) properties of K2Ca2(SO4)3:Eu nanoparticles by swift heavy ions (SHI), irradiation is studied. Pellets form of the nanomaterials were irradiated by 48 MeV Li3+, 75 MeV C6+, and 90 MeV O7+ ion beams. The fluence range is 1×109−1×1013 ions/cm2. The modification in TL glow curves of the nanomaterials irradiated by Li3+, C6+, and O7+ ion beams are essentially similar to those induced by γ-ray irradiation. These glow curves have single peaks at around 427 K with a small variation in their positions by around ±3 K. The TL intensity of the ion beams irradiated nanomaterials is found to decease, while going from low to high atomic number (Z) ions (i.e., Li3+→O7+). The TL response curve of the pellets irradiated by Li3+ ions is linear in the whole range of studied fluences. The curves for C6+ and O7+ irradiated samples are linear at lower fluences (1×109–1×1012 ion/cm2) and then saturate at higher fluence. These results for the nanomaterials are much better than that of the corresponding microcrystalline samples irradiated with a Li3+ ion. The curves were linear up to the fluence 1×1011 ion/cm2 and then become sublinear at higher fluences. The TL efficiency values of K2Ca2(SO4)3:Eu nanoparticles irradiated by 48 MeV Li3+, 75 MeV C6+, and 90 MeV O7+ ion beams have been measured relative to γ rays of C60o and are found to be 0.515, 0.069, and 0.019, respectively. This value for the Li3+ ion (0.515) is much higher than that of the corresponding microcrystalline material (0.0014). These superiorities for the nanomaterials make K2Ca2(SO4)3:Eu nanophosphor a suitable candidate for detecting the doses of swift heavy ions. PL studies on the ion beams irradiated and unirradiated K2Ca2(SO4)3:Eu nanoparticles show a single band at 384 nm, which could be assigned to Eu2+ emission, while the microcrystalline form of this material shows emission at 436 nm. This wide blueshift in PL of the nanomaterial could be attributed to the extension of the band gap of Eu2+ due to the absence of crystal field effects.
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