Their Thermoluminescence Research Articles

Thermoluminescence kinetics of undoped and doped (Ti, Cu, Ce) lithium aluminate crystals

Lithium aluminate (LiAlO2) crystals, both undoped and doped with Ti, Cu and Ce, were grown using the Micro Pulling Down method and their thermoluminescence (TL) was studied. The first order kinetics of thermoluminescent glow curves was confirmed. The Tmax-Tstop method showed the existence of a high number of overlapping peaks. The same conclusion followed from the deconvolution of TL glow curves. We show that TL signal consists of at least 9 overlapping peaks. Comparison of trap parameters obtained with deconvolution and the variable heating rate method is presented.

Luminescence properties of Na2Sr2Al2PO4Cl9:Sm3+ phosphor

A series of Sm3+ ions doped Na2Sr2Al2PO4Cl9 phosphors were synthesized via solid state synthesis method. Photoluminescence (PL) emission spectra were obtained by keeping excitation wavelength at 406nm. Emission spectra show three emission peaks at 563nm, 595nm and 644nm. The CIE chromaticity diagram shows emission colour of the phosphor in the orange-red region of the visible spectrum, indicating that the phosphor may be useful in preparing orange light-emitting diodes. Na2Sr2Al2PO4Cl9:Sm3+ phosphors were irradiated by γ-rays from a 60Co source and β-rays from a 90Sr source. Their thermoluminescence (TL) glow curves were obtained by Nucleonix 1009I TL reader. TL Trapping parameters such as activation energy of trapped electrons and order of kinetics were obtained by using Chen's peak shape method, Glow curve fitting method and initial rise method.

Luminescence features of dysprosium and phosphorus oxide co-doped lithium magnesium borate glass

Lithium magnesium borate (LMB) glass system co-doped with the oxides of dysprosium (Dy2O3) and phosphorus (P2O5) were synthesized using melt-quenching method. Prepared samples were characterized using various techniques to determine the effects of co-dopants concentration variation on their thermoluminescence (TL) and photoluminescence (PL) properties. TL glow curves of LMB:0.5Dy sample revealed a single prominent peak at Tm=190°C, where TL intensity was enhanced by a factor of 2.5 with the increase of P2O5 concentration up to 1mol%. This enhancement was accompanied by a shift in Tm towards higher temperature. Good linearity in the range of 1–100Gy with linear correlation coefficient of 0.998 was achieved. PL spectra displayed two significant peaks centred at 481nm and 573nm. These attractive luminescence features of the proposed glass system may be useful for the development of radiation dosimetry.

Thermoluminescence and photoluminescence properties of NaCl:Mn, NaCL:Cu nano-particles produced using co-precipitation and sono-chemistry methods

The NaCl: Cu and NaCl: Mn nanoparticles (NPs) were produced by co-precipitation and sono-chemistry methods and their thermoluminescence (TL) and photoluminescence (PL) properties were studied. By decreasing the particles size a considerable increase in sensitivity of the samples to high dose gamma radiation was observed. The NPs produced by sono-chemistry method have smaller size, homogeneous structure, more sensitivity to high gamma radiation and less fading than of those produced by co-precipitation method.

Change in thermoluminescence behaviour of cubic Gd2O3:Yb3+ phosphors with successive increase in Yb3+ ion concentrations

Nanocrystalline Yb3+ doped Gd2O3 phosphors were synthesized by solid state reaction method (SSRM), and effect of Yb3+ concentrations (1mol% to 7mol%) on thermoluminescence properties were studied. The XRD technique shows the cubic structure of prepared phosphor for different concentrations of Yb3+. No phase change was found due to the dopant concentration. The crystal size was calculated by Scherer's formula, which is found in 20–60nm range. The same was also confirmed from the field emission gun scanning electron microscopy (FEGSEM) image, which shows the formation of nanospheres having diameter 20–60nm range. They are found to be quite uniform in shapes and sizes. Functional group analysis was studied by Fourier transform infrared spectroscopy (FTIR) techniques and the elemental analysis of prepared phosphor was studied by energy dispersive X-ray spectroscopic (EDX) analysis. The samples were irradiated with UV and gamma radiation for the doses varying from 5 to 30min for UV and 0.5kGy to 2kGy for gamma respectively and their thermoluminescence (TL) characteristics have been studied. The effect of heating rate (3–7°Cs−1) and effect of Yb3+ concentration in TL glow curve have been studied. The TL glow curve of nanophosphor shows a peak at around 130°C for UV and at 247°C for gamma irradiation respectively. The TL response of the sample irradiated with different gamma doses shows a linear behaviour from 0.5kGy to 2kGy and become sublinear behaviour in the range of 5–25min UV exposure before it saturates with further increase in the dose. Simple glow curve structure, easy method of synthesis and the linear dose response make the nanocrystalline phosphor a good candidate for radiation dosimetry, especially for the estimation of high doses of gamma rays where the nanocrystalline phosphors generally saturated.

X‐ray computed tomography imaging: A not‐so‐nondestructive technique

AbstractX‐ray computed tomography has become a popular means for examining the interiors of meteorites and has been advocated for routine curation and for the examination of samples returned by missions. Here, we report the results of a blind test that indicate that CT imaging deposits a considerable radiation dose in a meteorite and seriously compromises its natural radiation record. Ten vials of the Bruderheim L6 chondrite were placed in CT imager and exposed to radiation levels typical for meteorite studies. Half were retained as controls. Their thermoluminescence (TL) properties were then measured in a blind test. Five of the samples had TL data unaltered from their original (~10 cps) while five had very strong signals (~20,000 cps). It was therefore very clear which samples had been in the CT scanner. For comparison, the natural TL signal from Antarctic meteorites is ~5000–50,000 cps. Using the methods developed for Antarctic meteorites, the apparent dose absorbed by the five test samples was calculated to be 83 ± 5 krad, comparable with the highest doses observed in Antarctic meteorites and freshly fallen meteorites. While these results do not preclude the use of CT scanners when scientifically justified, it should be remembered that the record of radiation exposure to ionizing radiations for the sample will be destroyed and that TL, or the related optically stimulated luminescence, are the primary modern techniques for radiation dosimetry. This is particularly important with irreplaceable samples, such as meteorite main masses, returned samples, and samples destined for archive.

TL response of Eu activated LiF nanocubes irradiated by 85 MeV carbon ions

Carbon ions were found to be effective for cancer treatment. These heavy ions have a high relative biological effectiveness compared to those of photons. They have higher linear energy transfer and sharper Bragg peak with a very excellent local tumor control. However, the dose of these swift heavy ions needs to be measured with great accuracy. Lithium fluoride (LiF) is a highly sensitive phosphor widely used for radiation dosimetry. In this work Eu activated LiF nanocubes were exposed to 85MeV C6+ ion beam and evaluated for their thermoluminescence (TL) response. Pellet forms of this nanomaterial were exposed to these ions in the fluence range 109–1013ions/cm2. The obtained result shows a prominent TL glow peak at around 320°C, which is different than that induced by gamma rays. This glow peak exhibits a linear response in the range 109–1012ions/cm2, corresponding to the equivalent absorbed doses 0.273–273kGy. The absorbed doses, penetration depths and main energy loss were calculated using TRIM code based on the Monte Carlo simulation. The supralinearity function and stopping power in this nanomaterial were also studied. The modification induced in the glow curve structure as a result of changing irradiation type might be utilized to use LiF:Eu nanocubes as a dosimeter for mixed filed radiations. Moreover, the wide linear response of LiF:Eu nanocubes along with the low fading are another imperative results suggesting that this nanomaterial might be a good candidate for carbon ions dosimetry.

Thermoluminescence and photoluminescence analyses of MEH-PPV, MDMO-PPV and RU(bpy)3 gamma-irradiated polymer thin films

Effects of irradiation with 60Co gamma photons on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), poly[2-methoxy-5-(3′,7′ dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (Ru(bpy)3) thin films were analyzed regarding their thermoluminescence (TL) and photoluminescence (PL) properties. A linear TL dose response was obtained from the MEH-PPV and MDMO-PPV polymer films in dose ranges of approximately 0.170–4.08kGy and 0.170–0.850kGy, respectively, followed by a supralinear behavior. A dependence on the conjugation length of the polymer chains which was favored by heating of the film, was observed, and irradiation generated a blue-shift in MEH-PPV and Ru(bpy)3. Furthermore, the PL structure was not modified. The most likely effect involved in the TL emission was trapping. The high activation energy values of the traps in the TL may be attributed in part to the binding energy of the exciton. A deconvolution process was carried out to obtain the kinetic parameters from the TL glow curves and PL spectra.

Synthesis and Thermoluminescence of Scandium-Titanium Based Oxide Mixture

ABSTRACTRecently, the research team synthesized some scandium- and titanium-based oxide compounds, in order to analyze their thermoluminescent (TL) response [1-2]. The oxides mixture Sc2TiO5:Eu2Ti2O7:Sc2O3 was synthesized in equilibrium phase by solid state reaction at 1100 °C / 48 h. The structural characterization was performed by XRD and SEM. The TL properties of this oxide mixture were examined after exposing it to gamma radiation from a 60Co source. The glow curve showed two main glow peaks at 151 °C and 260 °C, yet the curve shape looks quite complex, revealing that it is composed by overlapped individual TL peaks, which was confirmed with the Tstop preheat method performed [3]. The linear dose-response between 150 to 600 Gy was obtained, followed by a slow saturation stage. The intensity of the glow curves increases as the radiation dose increases, and their maxima remain at the same temperature values, which indicates that the TL phenomenon follows first-order kinetics [4]. After ten irradiation-TL readout cycles at 500 Gy, good stability (SD 2.02 %) between TL integrated response and the exposure dose was found. It is concluded that Sc2TiO5:Eu2Ti2O7:Sc2O3 is a promising material to use as high-dose dosimeter.

Study of Traps in Special Doped Optical Fiber Radiation Sensors via Glow Curve Analysis

Thermoluminescence dosimeters (TLDs) are widely used, serving the needs of various radiation applications. In recent times optical fibers have been introduced as alternatives to more conventional phosphor-based TLD systems, with many efforts being carried out to improve their thermoluminescence (TL) yield. While there have been extensive studies of many of the various TLD characteristics of optical fibers, including TL response, linearity, reproducibility, repeatability, sensitivity and fading, far more limited studies have concerned dependence on the type of TL activator used in optical fibers, promoting the TL mechanism. Present study focuses on TLD glow curves analysis for five different doped optical fibers that have been subjected to photon and electron irradiation. Trap parameters such as activation energy and frequency factors have been obtained from second order kinetics analysis, based on computerized glow curve deconvolution. An interesting observation is that co-doped fibers typically leads to enhanced TL characteristics, pointing to a need for optimization of the choice and levels in use of co-dopants.

Luminescence Properties of CaF2 Nanostructure Activated by Different Elements

Nanostructures of calcium fluoride (CaF2) doped with Eu, Tb, Dy, Cu, and Ag were synthesized by the coprecipitation method and studied for their thermoluminescence (TL) and photoluminescence (PL) properties. The PL emission spectrum of pure CaF2 nanostructure has a broad band in the 370–550 nm range. Similar spectra were observed in case of doped samples, beside extra bands related to these impurities. The maximum PL intensity was observed in Eu doped sample. The TL results of Eu, Cu, Ag, and Tb doped samples show weak glow peaks below 125°C, whereas Dy doped one is found to be highly sensitive with a prominent peak at 165°C. This sample was further exposed to a wide range of gamma rays exposures from 137Cs source. The response curve is linear in the 100 Gy‐10 kGy range. It is also observed that the particle size of CaF2 nanostructure was significantly reduced by increasing Dy concentration. These results showed that Dy is a proper activator in the host of CaF2 nanostructure, providing a highly sensitive dosimeter in a wide range of exposures and also plays a role as a controlling agent for particle size growth.

Thermoluminescence studies on single crystal, polycrystalline and glass lithium tetraborate samples irradiated by X-rays from Indus-2

Undoped, Mn doped and Cu doped samples of lithium tetraborate (LTB) were prepared in single crystal, polycrystalline and glass forms. These samples were investigated for their thermoluminescence (TL) response on irradiation by X-rays from Indus-2 synchrotron radiation source. Two well separated peaks were observed in TL glow curves for the doped single crystal and polycrystalline samples; however, glass samples show only one peak. Activation energy, frequency factor and order of kinetics were determined from the TL glow curve. Cu doped LTB crystal sample was found most TL sensitive whereas undoped LTB glass gives the least TL counts. Compared to doped samples, the undoped LTB glass sample was found suitable for high dose measurement immediately after irradiation.

Thermoluminescence properties of sintered ZnO

New pellet-shaped ZnO phosphors were synthesized using a controlled chemical reaction. Some samples were sintered at 1123, 1173 or 1223K during 24h in air, and then exposed to beta particle irradiation in the dose range from 25 to 800Gy to investigate their thermoluminescence (TL) properties. By considering their sensitivity, reproducibility, and fading features, samples sintered at 1173K exhibit the best dosimetric characteristics. From computerized glow curve deconvolution that was carried out using a general order equation, the kinetics parameters were computed, and it was found that the glow curves are composed by six individual TL peaks with kinetics order ranging from 1.2 to 1.8.

Synthesis and Characterization of Novel ZnO Nanophosphors

In this paper, the novel ZnO nanophosphors is synthesized by solgel method. The study exposed ZnO nanophosphors samples in Gamma (y) radiation to investigate their thermo-luminescence (TL) intensity as a function of temperature. The thermo-luminescence response has been studied in the dose range 0.291.16 kGy and it is observed that the thermo-luminescence response increases with increase in the dose. Moreover, the TL intensity increases with temperature and attains its maximum value near 200 Cand decreases after this temperature. Keywords: Dosimetry; Thermo-luminescence; Zinc oxide; Nanophosphors.

Thermoluminescence dosimetry properties and kinetic parameters of lithium potassium borate glass co-doped with titanium and magnesium oxides

Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of 60Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230°C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Zeff=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 103 Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software.

Thermally stimulated luminescence of Mg-doped ZnO Nanophosphors

Nanosized ZnO:Mg phosphors were synthesized through a controlled chemical reaction. X-ray diffraction patterns confirmed that Mg entered in a substitutive way in Zn sites. To investigate their thermoluminescence (TL) properties, some samples were exposed to beta-particle irradiation. The results reported here show that Mg doping improves ZnO TL features that are important for TL dosimetry applications, such as the shape of the glow curve, the temperature at which the maximum TL intensity is observed, and the TL fading and reproducibility. No saturation clues of the TL response as a function of the dose is observed for doses below 1600 Gy.

Characterization and luminescence studies of Eu doped Barite nanophosphor

Barite (BaSO4) nanophosphors were successfully prepared by the co-precipitation method. The structural analysis of the sample was carried out by analytical techniques such as X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. XRD study reveals that the particles exhibit orthorhombic structure and are approximately 50nm in size, while TEM study further confirms the particle size in the range 48–52nm and depicts oval shape of the particles. The FTIR spectrum displays the bands centered at 1197 to1077cm−1 and the shoulder at 982cm−1 corresponding to the symmetrical vibration of SO42− ion. Moreover, S–O bending and stretching are the Raman signature of barite, which were proven by the Raman spectra, unveiling the various vibrational modes of the compound. Samples were irradiated by gamma rays and proton beams and their Thermoluminescent (TL) glow curves were plotted and studied. On applying two different types of irradiations in addition to large energy difference, the sample showed almost a similar TL glow curve structure, which is the remarkable feature of this phosphor. Analysis of the glow curve was also carried out by the glow curve deconvolution method. Photoluminescence (PL) study shows broad excitation spectra with the main peak at around 250nm whereas the emission band excited by the wavelength 250nm was observed at 374nm which corresponds to the 4f65d→4f7 (8S7/2) transitions of Eu2+ ions. The sample was also examined for its PL response to different exposures of gamma irradiations where it showed an increase in the PL intensity up to a dose of 800Gy for both excitation and emission spectra. The present sample shows good crystal quality along with high TL and PL sensitivity. Hence our results suggest possible potential applications of nanocrystalline BaSO4:Eu phosphor in dosimetric study of gamma and proton beams.

Comparison of thermoluminescence spectra of MgB4O7 doped with dysprosium and manganese

A series of magnesium borate phosphors MgB4O7:Dy, MgB4O7:Mn and MgB4O7:Dy, Mn were prepared and their thermoluminescence (TL) emission spectra were measured. TL emission bands in 480, 575 and 660 nm at 200 and 360 °C were observed in the MgB4O7:Dy due to the transitions of the trivalent rare earth ions Dy3+. The glow peaks of broad wavelength band around ∼580 nm at 180 and ∼290 °C were observed in MgB4O7:Mn due to the emission of Mn2+ ions. The main glow peak of MgB4O7 co-doped with Dy and Mn appeared in 580 nm at ∼360 °C. When MgB4O7 was co-doped with Dy (0.5 mol.%) and different concentrations of Mn (0.01 mol.%–1.0 mol.%), the peak in 580 nm at 360 °C was intensified and broadened as the concentration of Mn increased, while the peaks in 480, 680 and 750 nm below 300 °C remained the characteristic emission of Dy3+ and were reduced in intensity. The emission spectra of the MgB4O7:Dy, Mn phosphor showed that the competitive de-excitation processes between Dy3+ and Mn2+ existed and the energy transfer occurred from Dy3+ to Mn2+. These results meant that rare earth and Mn ions in MgB4O7:Dy, Mn might cause the formation of defects complex that dominated the traps and recombination.

Study of TL and optically stimulated luminescence of K2Ca2(SO4)3:Cu nanophosphor for radiation dosimetry

Nanocrytstalline K2Ca2(SO4)3:Cu phosphor was synthesized by the chemical co-precipitation method and annealed at different temperatures (400–900°C) for 2h. The XRD spectrum shows the cubic structure with crystallite size ~20nm. The same was also confirmed from the TEM image which shows the formation of nanorods having diameter ~20nm and length of ~200nm. They are found to be quite uniform in shapes and sizes. These samples were irradiated with gamma radiation for the doses varying from 0.01Gy to 10kGy and their thermoluminescence (TL) characteristics and continuous wave optically stimulated luminescence (CW-OSL) have been studied. The sample annealed at 700°C was found to be most sensitive than others. The glow curves of the nanophosphor show a major peak at around 175°C and other two peaks of low intensity at around 85°C and 305°C. The traps responsible for the three thermoluminescence peaks in K2Ca2(SO4)3:Cu are also found to be sensitive to the OSL. The qualitative correlation between TL peaks and CW-OSL response is established. The TL response of the sample annealed at 700°C for 2h and irradiated with different gamma doses shows a linear behavior from 0.01 up to 300Gy and become sublinear in the range of 300 Gy–1kGy before it saturates with further increase in the dose, while, the OSL response of the same sample shows linearity up to 1kGy. Simple glow curve structure, easy method of synthesis, and linear dose response make the nanocrystalline phosphor a good candidate for radiation dosimetry, especially for the estimation of high doses of gamma rays where the microcrystalline phosphors generally saturate.

TL characterization of CVD diamond films deposited at different growth parameters

Diamonds can be used as dosimeters due to their high sensitivity to the ionizing radiation, radiation hardness as well as mechanical and chemical resistance. Moreover diamond, as the allotropic form of carbon, is tissue‐equivalent what is an important property in regard to its potential future application in medical physics. Diamond films deposited on Si substrates by chemical vapor deposition (CVD) method using SEKI plasma reactor at the Institute of Nuclear Physics in Krakow were investigated to the aspect of their thermoluminescent (TL) properties. The deposition was performed at different oxygen concentration and the thermoluminescence of diamond films was studied. All grown diamond films were characterized in terms of surface morphology (scanning electron microscopy), chemical (Raman spectroscopy) and structural properties (X‐ray diffraction). The influence of three types of radiation: α (241Am, 5.49 MeV), β (90Sr/90Y, 2.27 MeV), γ (60Co, 1250 keV) on the shape of the TL curves was also examined.