Their Thermoluminescence Research Articles

Thermoluminescence study of MnO doped borophosphate glass samples for radiation dosimetry

MnO doped calcium fluoroborophosphate glasses of the composition 20 CaF2–50 P2O5–(30−x)B2O3:x MnO in mol% with x ranging from 0.2 to 1.0 (in steps of 0.2) were synthesized. The samples were exposed to different γ-ray doses in the range 250–1000Gy and their thermoluminescence (TL) was recorded in the temperature range ambient to 300°C. The glow curves of all these samples exhibited an intense principal peak at about 200°C followed by a feeble high temperature peak at about 300°C. The TL response of integral TL output as well as TL of the principal peak exhibited perfectly linear increase with the dose within the range of 250–1000Gy. However, the gradual increase of MnO content in the glass matrix caused a decrement in the TL output. Such mechanism is explained based on different valence states of Mn ions in the glass matrix and the quenching effect is assumed to be well exploited to measure the high radiation doses required in radiation processing facilities without saturating the PMT of the reader. The comparison of TL response of the studied glasses with that of CaSO4:Dy phosphor indicated an improvement in the dose response in terms of linearity and adequate sensitivity for the measurement of high doses.

Development of high sensitive LiNaSO4:Cu,Mg phosphor for TLdosimetry

LiNaSO4:Cu and LiNaSO4:Cu,Mg low Z phosphors (Zeff=11.59) are synthesized by wet chemical route and exposed to γ-rays of 60Co for their thermoluminescence (TL) study. The XRD technique showed the crystalline nature of the prepared material. Photoluminescence studies have been undertaken to ensure the successful incorporation of Cu and Mg impurities in LiNaSO4 host lattice. The induced TL glow curves of LiNaSO4:Cu and LiNaSO4:Cu,Mg samples are found at 166°C and 160°C with single peak respectively. The TL intensity was found to be enhanced nearly two times by co-doping of Mg in LiNaSO4:Cu. The prepared phosphors have a linear response, less fading and excellent reusability. The whole glow curve displays a good stability under storage at room temperature. Comparison of TL intensity of the most intensive glow peak of LiNaSO4:Cu,Mg with that of standard TLD CaSO4:Dy shows that their intensities are almost equal. The trap parameters namely order of kinetics (b), activation energy (E), frequency factor (s) and Balarin parameter (γ) associated with the most intensive glow peak, i.e. 160°C glow peak of LiNaSO4:Cu phosphors were determined by using glow curve shape (Chen's) method. The deconvolution of the glow curve was done by using computerized glow curve deconvolution (CGCD) technique.

Cu+ emission in Li2BPO5 material for thermoluminescence dosimetry

In this study, Li2BPO5 doped with Cu and that co-doped with Mg are synthesized by the wet chemical technique and exposed to γ rays of 60Co to determine their thermoluminescence (TL) properties. The X-ray diffraction technique shows the crystalline nature of the prepared material. The photoluminescence (PL) emission spectra of Li2BPO5:Cu phosphor show the strong prominent peak at 368 nm in the violet region of the visible spectrum due to the transition of 3d94s1 ↔ 3d10 of monovalent copper ion. The PL emission of Li2BPO5:Cu is enhanced by the addition of Mg. The TL glow curves of γ-irradiated Li2BPO5:Cu sample show one glow peak at 143°C, indicating that only one set of traps is being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The trapping parameters associated with the prominent glow peak of Li2BPO5:Cu are calculated using the glow curve shape (Chen's) method. The release of hole/electron from defect centers at the characteristic trap site initiates the luminescence process in these materials. A linear TL response is observed in Li2BPO5:Cu in a long span of exposures. The sensitivity of Li2BPO5:Cu sample is observed to be 7.8 times that of (TLD-100) LiF:Mg, Ti.

Thermoluminescence property of LiMgF3 erbium activated phosphor

The perovskite-like LiMgF3:ErF3 pellets were obtained from the melt formed by LiF and MgF2 mixed salts in the stoichiometric ratio. The perovskite material was doped with 1, 2 and 4mol% of ErF3 impurity. The pellets samples were 60Co gamma irradiated and their thermoluminescence (TL) properties were analyzed, i.e., dose–response, fading at RT and under UV irradiation, TL signal reproducibility, and kinetic parameters. The intensity of the TL response against irradiation dose was increased remarkably by the high concentration of impurity, and a linear dose–response was observed in the range of 1–10Gy. The fading observed at RT was about 10–30% after 24h from irradiation. All samples were exposed from 1 to 200Gy gamma dose range. The TL glow peaks were found around 367–376, 438–447, 509–521, and 594–611K, when the doped samples were 1, 2 and 4mol% of the erbium impurity concentration. The thermoluminescence kinetics parameters of the glow curves have been analyzed using the Computerized Glow Curve Deconvolution (CGCD) method.

Dating ancient mosaic glasses by luminescence: The case study of San Pietro in Vaticano

The preliminary results of a study on the dosimetric properties of a set of glass tesserae from the mosaics of the vaults of St. Peter’s Basilica in Rome (late XVI century) are reported. The main goal of the research was to assess the possibility of dating them by means of luminescence techniques. The samples had already been extensively studied and investigated from a historical, artistic and compositional point of view. The period of the making of the mosaic was rather well known, and could be the basis to test the experimental procedures we used for dosimetry. The experiments also aimed at demonstrating the validity of the hypothesis we put forward, i.e. the positive link between the presence of micro-crystals and the luminescence sensitivity in mosaic glass: to this aim, the samples richer in crystalline inclusions were selected. The role of calcium antimonate and cassiterite was definitely demonstrated. For what concerns their thermoluminescence (TL) characteristics, a preliminary investigation suggested that the available configuration of the detection systems did not properly fit the wavelength of the emitted TL. Much more promising results have been achieved by the use of Optically Stimulated Luminescence (OSL), even if the measured absorbed doses were rather scattered. For one sample with high OSL sensitivity, it was possible to establish its recent age, relative to one of the documented restorations that took place during the last century.

Luminescence characteristics of Li2NaBF6: Cu phosphor

Li2NaBF6 doped with Cu and co-doped with P are synthesized by wet chemical technique and exposed to gamma-rays of 60Co for their thermoluminescence (TL) properties. The XRD technique shows the crystalline nature of the prepared material. The induced TL glow curves of Cu doped sample are found to be at 118°C with a single peak. Li2NaBF6: Cu is low Z material (Zeff=8.96) and observed 4.3 times more sensitive than LiF: Mg, Ti (TLD-100). A linear TL response is observed in Li2NaBF6: Cu in a long span of exposures. The trap parameters namely order of kinetics (b), activation energy (E), frequency factor (s) and Balarin parameter (γ) associated with the most intensive glow peak, i.e. the 118°C glow peak of Li2NaBF6: Cu phosphor were determined by using glow curve shape (Chen’s) method and these parameters are in good agreement. Photoluminescence (PL) emission spectra of Li2NaBF6: Cu phosphor shows the strong prominent peak at 368nm in the violet region of the visible spectrum due to the transition of 3d94s1↔3d10 of Cu+ ion. The increase in photoluminescence of Li2NaBF6: Cu by co-doping with P has been studied.

Thermoluminescence of B 2O 3–Li 2O glass system doped with MgO

Lithium borate (LiB) glasses in the system (100− x)B 2O 3– xLi 2O with x=20, 30, 40, 50, 60 and 70 mol% were prepared. The glasses were doped with different concentrations of the order of 10 −1, 10 −2, 10 −3, 10 −4 and 10 −5 of MgO and their thermoluminescent (TL) response was investigated. The irradiations were performed using γ rays from a 60Co source in the dose range from 0.1 to 25 kGy. The material displayed good sensitivity for γ-rays and intensity of TL signals is dependent on γ-ray dose and Li 2O content. For each dose level and investigated temperature range (50–350 °C), exactly single isolated glow peak appears in the temperature range of 165–205 °C depending on both Li 2O concentrations and time of exposure. The shape of the glow peak has altered significantly with increase in the gamma ray dose or Li 2O concentrations. The glass composition with x=50 mol% doped with 10 −3 mol% of MgO presented the best TL response. The results of the present study indicated that the recorded single and isolated high temperature peak is a good candidate for TL dosimetric investigations. This indicates that 50 B 2O 3–50Li 2O-doped with 10 −3 mol% of MgO is possibly used as materials for radiation dosimetry in the dose range of 0.1–20 kGy.

Nanorods of LiF:Mg,Cu,P as Detectors for Mixed Field Radiations

Nanocrystalline powder of LiF: Mg,Cu,P phosphor has been synthesized by the chemical coprecipitation technique. Shape and size of these nanomaterials were observed by transmission electron microscope and atomic force microscope. The particles are of rod shapes having diameters from 50 to 80 nm and lengths varying within the range 0.4-0.7 mum. Pellets of these nanorods were irradiated by 48 MeV7Li3+ ions at different fluences in the range 1times1011-1times1014 ions/cm2 (with corresponding doses in the range 0.679-679 kGy) and their thermoluminescence (TL) properties have been studied. The TL glow curves are observed to have prominent peaks at around 588 K along with smaller one at around 410 K. The TL intensity of the former is found to increase with increasing the fluence, while that of the latter decreases. These behaviors are in contrast with those of the peaks induced by 137Cs gamma-rays. This modification in case of irradiation by ion beam has been attributed to the change in population of the luminescent/trapping centers due to the use of highly energetic ions. From these results, it is suggested that the nanorods of LiF:Mg,Cu,P might be used as detectors for mixed fields radiations such as space radiations.

Effects of Sr2+ doping on the persistent luminescence properties of CaAl2O4:Eu2+, Nd3+

To reveal the components of defects responsible for persistent luminescence properties of CaAl2O4:Eu2+, Nd3+, a slight amount of Sr2+ ions were doped in host lattice. Their thermoluminescence (TL) and decay curves were investigated. The results showed that the concentration of traps in CaAl2O4:Eu2+, Nd3+ decreased linearly with the increase in Sr2+. Furthermore, both of their initial luminance and decay time also decreased. As Sr2+ ions preferred to occupy Ca2+ vacancies, the suppression of TL and persistent luminescence reflected that some isolated Ca2+ vacancies might be acting as bridges to transport carriers between trapping centers and emission centers. On the basis of these results, the manner of carriers’ transport in CaAl2O4:Eu2+, Nd3+ is discussed in detail, and a possible structural defects unit is designed as well.

Photoluminescence and thermoluminescence characteristics of KXSO4Cl : Eu (X = Zn or Mg) halosulfate phosphor

Polycrystalline KZnSO4Cl : Eu and KMgSO4Cl : Eu prepared by a wet chemical method have been studied for their thermoluminescence (TL) and photoluminescence (PL) characteristics. The PL emission spectra of the phosphor suggests the presence of Eu2+ and Eu3+ in the host compound occupying two different lattice sites. The TL glow curve of the KZnSO4Cl : Eu compounds has a simple structure with prominent peaks at 200 and 290 °C, while KMgSO4Cl : Eu peaks at 165 and 265 °C. The TL sensitivity of the phosphors is compared with CaSO4 : Dy and is found to be 3.4 and 2.4 times less in KZnSO4Cl : Eu and KMgSO4Cl : Eu phosphors, respectively.

Thermoluminescence of aluminophosphate glasses in the metaphosphate composition

Potassium aluminum phosphate (KAP) glasses in the system xKPO 3–(100 − x)Al(PO 3) 3 with x = 10, 30 and 50 mol% were prepared in the metaphosphate composition. The glasses were doped with MnO 2 and their thermoluminescent (TL) response was investigated. Raman spectra showed that these glasses did not undergo structural changes with the substitution of manganese ions. The glass composition x = 50 mol% doped with 1.0 mol% of MnO 2 presented the best TL response. The material displayed good sensitivity for γ-rays, X-rays and UV light. The emission curves exhibited two TL peaks, one at a low temperature (∼150 °C) and the other at a high temperature (∼365 °C), whose positions were dependent on the type of exciting radiation applied. The results of the present study indicated that the high temperature peak is a good candidate for TL dosimetric investigations.

Thermoluminescence properties of CVD diamond films

Two kinds of CVD diamond films were investigated with respect to their thermoluminescent (TL) properties, especially concerning their sensitivity to ionising radiation and to daylight. The films were characterised by means of Raman/photoluminescence/FTIR spectroscopy, XRD, RBS and elastic recoil detection analysis (ERDA). Thermoluminescent (TL) responses of these materials to photons provided by radionuclide 55Fe source (≈6 keV) over the dose range from 1 to 100 mGy were measured. Typical TL glowcurve is a result of two components, one with maximum in range 160–180 °C and the second, between 307–327 °C. In irradiated samples, the first peak is caused by the exposure to daylight, which increases overall TL signal, the second is caused by irradiation by ?-photons. Exploitation of TL properties of CVD diamonds for a photon dosimetry is possible after careful daylight shielding. The sensitivity of used CVD diamond dosimeters was 10 times less than that of TLD 100 (LiF: Mg, Ti) Harshaw dosimeter. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A Study of the Thermoluminescent Properties of CVD Diamond Detectors

A batch of 20 diamond detectors obtained by the chemical vapour deposition (CVD) method at the Institute for Materials Research at the Limburg University, Belgium, was investigated with respect to their thermoluminescent (TL) properties. The investigated detectors demonstrate TL sensitivity similar to that of the standard LiF : Mg, Ti (MTS) thermoluminescent detectors, lack of fading after two weeks from irradiation and apparent linearity of dose response. In spite of the persistent fluctuation of individual detector sensitivity observed in this batch, a new annealing procedure improved the stability of the TL signal. It has been concluded that 1 h annealing at 350 °C assures the highest reproducibility for this set of detectors. A 30% discrepancy of the value of the TL signal between individual detectors from the batch may be caused by non-uniform distribution of dopants in the volume of the CVD diamond. A prototype of a planar TL reader equipped with a CCD camera was employed in this investigation.

Correlation between OSL and the distribution of TL traps in Al2O3:C.

Al2O3:C single crystals are known to exhibit some variation of their thermoluminescence (TL) glow curve shape from sample to sample. This variation is attributed to the fact that the TL peak in Al2O3:C is produced by the set of several traps. It is important to understand what part of the trap distribution correlates with the optically stimulated luminescence (OSL) process in this material. Crystals with a difference in the full-width, half-maximum (FWHM) of the TL peak as big as 30% and crystals having double-peak glow curves were used in this study. It was found that bleaching with a wavelength longer than 525 nm depletes mostly the low temperature part of the TL glow curve, leaving the high temperature peak unaffected. It was shown that when the pre-irradiation annealing temperature was increased from 500 to 1000 degrees C, the high temperature part of the abnormal double peak disappears. The phototransferred luminescence (PTTL) processes and conversion of F and F+ centres were also studied for samples having different glow curves shape. The practical aspect of this research is important for OSL dosimetry, because such crystals with wide or double TL peak can make it difficult to bleach OSL dosemeters for very low dose measurements.

Thermoluminescence of MgSO4 doped with Eu and P impurities.

CaSO4:Eu, MgSO4:Eu and MgSO4:Eu,P phosphors have been prepared and their thermoluminescence (TL) characteristics were studied. A main glow peak due to Eu2+ ions is seen at approximately 146 degrees C and 440 nm and glow peaks at approximately 145 degrees C, approximately 190 degrees C, approximately 260 degrees C and approximately 360 degrees C for 590 nm and 625 nm wavelengths are identified as Eu3+ ion emissions in MgSO4:Eu. Emission spectra in MgSO4:Eu and the MgSO4:Eu,P show that the MgSO4:Eu3+ glow peak at 260 degrees C for 590 nm and 625 nm shifts to 280 degrees C with enhanced intensity while the Eu2+ ion glow peak at 146 degrees C remains but with reduced intensity. The main glow peak at approximately 146 degrees C and 440 nm from Eu2+ ions shows significant difference from the characteristic glow peaks of Eu3+ ions. It is observed that the wavelength of the Eu2+ ion glow peak is inversely proportional to the radius of the cation of the host sulphate in alkaline-earth sulphate phosphors. By contrast the wavelengths of the Eu3+ ion glow peaks remain unchanged in different sulphates. Besides, the glow curve at approximately 146 degrees C obtained using a conventional blue sensitive reader shows simply the first order kinetics. It is concluded that the luminescence centres and distribution of traps related to Eu2+ ions are different from that of Eu3+ ions in MgSO4:Eu and MgSO4:Eu,P phosphors.

Investigation of the TL mechanism and defect structure in MgSO 4 doped with Eu and Mn, P impurities

Four phosphors CaSO 4:Eu; MgSO 4:Eu; MgSO 4:Eu,Mn and MgSO 4:Eu,P have been prepared and their thermoluminescence (TL) spectra were obtained. For MgSO 4:Eu a main glow peak due to Eu 2+ ions is seen at ∼144°C and 440 nm while for CaSO 4:Eu this occurs at ∼144°C and 390 nm . Further MgSO 4:Eu glow peaks at ∼145° C, ∼190° C , ∼260°C and ∼360°C for 590 and 620 nm wavelengths are identified as Eu 3+ ion emissions. These characteristic glow peaks occur at almost the same temperatures as in MgSO 4:Dy. In MgSO 4:Mn glow peaks at 140°C and 190°C for a broad wavelength band about 660 nm are seen from the Mn ions. When MgSO 4 is co-doped with Eu and Mn the Eu 2+ and Eu 3+ ion glow peaks are remarkably suppressed while the 660 nm broad emission band glow peaks at ∼140°C and 190°C remain with high intensity contributed from the Mn luminescence centers. Emission spectra in MgSO 4:Eu and the MgSO 4:Eu,P show that the MgSO 4:Eu 3+ glow peak at 260°C for 590 and 620 nm shifts to 280°C, while the Eu 2+ ion glow peak at ∼144°C remains but with reduced intensity. Thus, the effect of the P co-dopant in MgSO 4:Eu,P is exactly similar to its role in MgSO 4:Dy,P, i.e. shifting the 260°C peak to 280°C with enhanced intensity and suppressing the intensity of the other peaks. The main glow peak at ∼144°C and 440 nm from Eu 2+ ions shows significant difference from the characteristic glow peaks of Eu 3+ ions. It is found that the wavelength of the Eu 2+ ion glow peak is inversely proportional to the radius of the cation of the host sulfate. By contrast the wavelengths of the Eu 3+ ion glow peaks remain unchanged in different sulfates.

Optically stimulated luminescence in KMgF/sub 3/:Ce/sup 3+/ comparison of dosimetric characteristics with Al/sub 2/O/sub 3/:C

Ce/sup 3+/ doped KMgF/sub 3/ crystals have been investigated as a new material for dosimetry of ionizing radiation. Previous studies have focused on their thermoluminescence (TL) properties. This paper shows that the stored energy in this compound can also be read by visible light. Its sensitivity was found to be one order of magnitude greater than Al/sub 2/O/sub 3/:C, which can be considered as the standard dosimetric material based on optically stimulated luminescence (OSL). The greater sensitivity was due to a larger wavelength difference between stimulation and emission wavelengths, which results in a better separation of useful signal from scattered light. Time response characteristics were also significantly better than Al/sub 2/O/sub 3/:C, which allows in principle fast pulsed and multiple readouts. Unfortunately, the high self-dose (/spl sim/1.5 /spl mu/Gy/h) due to the natural abundance of /sup 40/K isotope is a major drawback for the application of this material in environmental dosimetry. Some features of the mechanism have been studied with different spectroscopic techniques. The luminescent centers have been clearly identified with Ce/sup 3+/ ions. It has been shown that the main trapping centers involved in OSL mechanism are the same as those involved in TL mechanism.

Influence of UV Light on the Thermoluminescence of CVD Diamond Detectors Irradiated by Ionizing Radiation

Two kinds of CVD diamonds (De Beers Company) were investigated with respect to their thermoluminescent (TL) properties, especially concerning their sensitivity to UV light. Both types of CVD diamond detectors irradiated by ionising radiation are sensitive to UV light (254 nm and 345-400 nm) and to daylight. The UV light sensitivity of CVD diamond detectors irradiated by ionising radiation disturbs the TL signal, either by diminishing the total TL output, or by introducing additional peaks, in which case the overall TL signal increases. To exploit the TL properties of CVD diamonds, it is recommended that they be totally shielded from light, i.e. handled in darkness.

Effect of gamma irradiation on thermoluminescence emissions from dust of Asian plant nuts

Experiments were conducted to see the effect of irradiation on the thermoluminescence emission from dust of plant nuts such as almond, peanut, pinenut and walnut. Inorganic dust particulate minerals adhering to the nut's surface were collected from unirradiated and irradiated (0.5, 1.0 and 1.5 kGy) samples, and analysed for their thermoluminescence (TL) intensities in the temperature range of 80-320 C at a temperature rate of 10 C/s. It was observed that peaks of the TL signals appeared at 200 C in each case and generally the magnitude of the peak signals of irradiated samples was manifold that of unirradiated controls. Regression and correlation analysis of the data indicated strong relationship between radiation adsorbed dose and TL values at each temperature (r ≥ 0.96). It was concluded that TL measurements could serve as a fast and reliable method for identifying as well as determining absorbed dose in irradiated plant nuts.

Thermoluminescence characteristics of quartz implanted by nickel ion

The implantation of artificial quartz with nickel ion has succeeded in using a heavy ion accelerator. The quartz with nickel ion is called ”nickel quartz“. The sensitivity of their thermoluminescence (TL) response to the beta radiation was decreased with the increasing of irradiating and heating times. Two TL characteristics have appeared: the sensitivity of TL response at lower temperature (ll0°C) peaks of the nickel quartz to beta radiation is higher than that of the pure quartz, this results from the Ni+1 ion entering the quartz lattice; and a new peak appearing at 445°C may be related with both Ni+1 and Ni+3.