In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited ... more In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.
Advances in Materials Science and Engineering, 2016
In this work, we report the thermoluminescence (TL) properties of self-agglomerating CaSO4:Eu sam... more In this work, we report the thermoluminescence (TL) properties of self-agglomerating CaSO4:Eu samples obtained by an environmentally friendly coprecipitation technique. No binding material is needed to form solid CaSO4:Eu samples. Samples exposed to beta particle irradiation exhibit a TL maximum at 473.15 K when a 5 K/s heating rate is used, they are two times more sensitive than the TLD-100 commercial dosimeter, and their lower detection limit was determined to be less than 0.69 mGy. The computerized glow curve deconvolution carried out fitting the residual glow curves from McKeever method revealed that the whole glow curve is composed of four individual TL peaks with intermediate-order kinetics. The main peak order kinetics is b = 1.48. This result agrees with that computed using Chen’s formula.
SiO 2 coatings prepared by the sol-gel method containing various amounts of copper have been anne... more SiO 2 coatings prepared by the sol-gel method containing various amounts of copper have been annealed under two different atmospheres to produce colloidal copper based particles embedded in a SiO 2 matrix. The particle composition depended on: the amount of copper added to the stating solutions, the atmosphere in which the samples were annealed and the annealing temperature. The optical properties of the colloidal coatings were determined using the model proposed by Mie, using effective values for the optical constants of the colloidal particles.
In this work, the thermoluminescence (TL) characterization of pellet-shaped ZnO:Na phosphors synt... more In this work, the thermoluminescence (TL) characterization of pellet-shaped ZnO:Na phosphors synthesized through a controlled chemical reaction followed by thermal annealing at 900°C in air is reported. X-Ray diffraction patterns reveal ZnO hexagonal zincite structure for the samples, some of which were exposed to beta particle irradiation in the dose range from 0.08 to 2048 Gy in order to study their TL features. The synthesized ZnO:Na samples are more than 200 times more sensitive than ZnO samples synthesized by the same method, and present a 0.02 (1/50) sensitivity relative to the TLD-100 dosimeter.
We have sintered an alkali halide KClXBr1-X:Eu2+ ceramics phosphors. These KClXBr1-X:Eu2+ are con... more We have sintered an alkali halide KClXBr1-X:Eu2+ ceramics phosphors. These KClXBr1-X:Eu2+ are considered as promising selective ultraviolet dosimeter material and they exhibit situable optical characteristics for using in digital radiography and optical memory devices. In this work, the thermoluminescence glow cuves were analized as a function of composition x. We have found that for intermediate compositions, around x = 0.6,
Diamond thin films were deposited onto Si (100) substrates using liquid a solution of water and a... more Diamond thin films were deposited onto Si (100) substrates using liquid a solution of water and acetone, ethanol, methanol and commercial Tequila as precursors by the Pulsed Liquid Injection Chemical Vapor Deposition (PLICVD) technique. Temperature was varied from 550 °C to 850 °C. In this work we attempted to find a crystal diameter dependence on temperature and pressure from the experimental data. The goal in this work is to found a function that can be adjusted to the experimental data.
Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of 90 Sr beta particles.... more Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of 90 Sr beta particles. The diamond thin films have been synthesized from commercial Tequila as a precursor using Pulsed Liq uid Injection by the Chemical Vapor Deposition (PLICVD) technique reported recently. Thermolumines cence (TL) phenomena at these doses exhibit peak curve shift to higher temperatures (from 370 to 440 K) in the glow curve and the integrated TL curve show a linear behavior. Therefore, it has been considered that diamond thin films could be used as high doses dosimeters.
In this work, the thermoluminescence (TL) features of Sc 2 O 3 exposed to beta particle irradiati... more In this work, the thermoluminescence (TL) features of Sc 2 O 3 exposed to beta particle irradiation in the dose range from 0.08 to 150 Gy are reported. Characteristic glow curves exhibit two main TL maxima, located at 74 and 192°C when a 2°C/s heating rate is used. The TL response as a function of dose exhibits a linear behavior for doses below 70 Gy. We conclude that Sc 2 O 3 is a promising phosphor material for using as TL dosimeter.
APPC 2000 - Proceedings of the 8th Asia-Pacific Physics Conference, 2001
The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to... more The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to X -rays or beta radiation. The main thermoluminescence (TL) peaks were found around 370, 390 and 470 K. The 470 K highest intensity peak is considered to be the dosimetric peak due to its low fading and linear dose behavior. The main dosimetric peak is sharply decreased after illumination with UV light of a previously irradiated specimen. The PTTL is wavelength dependent and has been shown to peak in the 220 - 230 nm region and 650 nm in previously non irradiated and irradiated samples, respectively. The PTTL spectral response is always a broad band around 390 - 490 nm peaked at 425 nm, which is related to the well-known Eu2+ emission.
Alkali halides crystals have been the subject of intense research for an understanding of their r... more Alkali halides crystals have been the subject of intense research for an understanding of their radiation-induced defects and luminescence properties. They exhibit noteworthy thermoluminescence (TL) properties when exposed to ionising radiation. Currently, these materials are grown employing expensive and rather complicated techniques. In this work, the results on the TL properties of new alkali halides phosphors fabricated by a simple and inexpensive procedure are presented. The samples were made by mixing KCl, KBr and EuCl3 salts, and compressing them at a pressure of 3.2 x 10(7) Pa during 3 min, followed by sintering at 700 degrees C during 24 h under air atmosphere. The dosimetric response of the samples showed an increase with radiation dose in the 1.5-20.0 Gy dose range for beta and gamma radiation. The TL glow curves in sintered samples presented significant differences in their peak structures compared with monocrystalline samples, indicating that the nature of the trapping states and the recombination mechanisms may be different.
Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by puls... more Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by pulsed-liquid injection chemical vapour deposition at 850 degrees C. Some samples were exposed to beta particle irradiation in the dose range from 100 to 1600 Gy, and it was found that the thermoluminescence (TL) response is a linear function of dose. The glow curve displays two maxima centred at 170 and 350 degrees C, which does not shift when dose changes, indicating that first-order kinetics processes are involved. From the results, it is concluded that the new nanodiamond films are promising high-dose TL dosimeters.
Hot filament chemically vapor deposited (HFCVD) boron doped diamond films were grown on monocryst... more Hot filament chemically vapor deposited (HFCVD) boron doped diamond films were grown on monocrystalline silicon (111) doped with B/C ratios of 4000, 8000 and 12,000 ppm. Scanning electron micrographs show that the films are composed of well-faceted microcrystallites ranging in size from about 1 to 5 µm with no correlation with B/C concentration. The Raman spectra exhibit a sharp diamond band at 1332 cm-1 which shifts to lower wave numbers, broaden and decreases as the B/C ratio increases. An additional broad band is observed around 1200 cm −1. The beta irradiated diamond films exhibit thermoluminescence (TL) and optically stimulated luminescence (OSL) and the TL glow curves can be fitted well with four glow peaks. The kinetic parameters of these TL peaks as well as their intensities depend on B/C ratio. The OSL curves of the diamond films grown with 4000 and 8000 ppm of B/C exhibit standard decay behaviour for continuos stimulation with light of 470 nm. However, the OSL signal of the 12,000 ppm film increases initially with light stimulation, reaching a maximum to decay afterwards.
Pellet-shaped NaF:Eu 3+ phosphors were synthesized by sintering. When a 5 K/s heating rate was us... more Pellet-shaped NaF:Eu 3+ phosphors were synthesized by sintering. When a 5 K/s heating rate was used, the characteristic glow curves of beta particle irradiated samples exhibited two thermoluminescence (TL) maxima located at 401 K and 498 K, being the higher temperature maximum the most intense. A peak located between 473 and 523 K is considered to have a position very suitable to assure good thermal stability of the stored TL, so this phosphor is attractive for radiation dosimetry. Beta particle irradiated samples displayed a TL response that increases as the radiation dose increased in the 0.08 to 42.5 Gy dose range, with a linear behavior below 10 Gy followed by a sublinear one for higher doses. Under storage after irradiation, the TL maximum at 498 K displayed a remarkable stability, and the TL fading revealed that the maximum at 401 K is not a single peak.
The thermoluminescence (TL) response of samples obtained from human teeth exposed to beta irradia... more The thermoluminescence (TL) response of samples obtained from human teeth exposed to beta irradiation shows that the characteristic glow curves exhibit TL emission at high enough temperatures, which ensures thermal stability of the TL signal, and the TL increases as the dose increases from 0.25 up to 128 Gy, with linear behavior for doses below 32 Gy. The dose interval tested is of interest for clinical applications. Samples do not suffer damage due to heating if the TL readouts are performed from room temperature up to 300 °C. W This indicate that human teeth are promising phosphor materials for use in different TL and afterglow dosimetry applications.
Keywords: Thermoluminescence; Human Teeth; Dosimetry; β - Irradiated Human Teeth; Hydroxyapatite.
In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited ... more In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.
In this work, we report on the afterglow (AG) response characterization of commercially available... more In this work, we report on the afterglow (AG) response characterization of commercially available ZrO 2. Pellet shaped samples previously annealed in air at 1000 °C during 24 h were exposed to beta particle irradiation in the dose range from 0.5 up to 128 Gy and their AG decay curves recorded during 600 s after irradiation exposure. The characteristic glow curves of beta particle irradiated ZrO 2 show two maxima located around 80 °C and 150 °C. The first one rapidly vanishes at room temperature, giving rise to AG. The integrated AG signal increases as dose increases from 0.5 to 128 Gy, with a linear dependence from 0.5 up to ca. 32 Gy. Excellent reproducibility of the AG response was observed in 10 irradiation-AG readout cycles, showing that the studied ZrO 2 samples are reusable. The results here presented show that ZrO 2 is a promising material for use as a radiation dosimeter based on the AG phenomenon.
We report the photoconductance of ZnO thin films obtained from thermally treated ZnS films grown ... more We report the photoconductance of ZnO thin films obtained from thermally treated ZnS films grown by a chemical bath deposition method. The measurements of photo-conductance were performed in an atmosphere of air or nitrogen (N 2) at different temperatures between 300 K and 375 K. The augmented conductance after ultraviolet (UV) irradiation (330-380 nm) in air fades away slowly to its original value, whereas in a nitrogen atmosphere, a significant part of the augmented conductance remains. Measurements of electrical conductance as a function of temperature in N 2 or air, in the dark or the light, seem to indicate that the donor concentration is increased during the UV irradiation, suggesting that oxygen vacancies and interstitials are created. An alternative model for the photoconduction in ZnO is proposed in which the slow increase of conduction during irradiation is explained by an increase of donors instead of photoelectrons. In this model, the photoelectrons would only play a role in the mechanism of the creation of donors.
The thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phospho... more The thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phosphors are presented. Pellet-shaped samples were prepared by cool-pressing 74 μm size particle powder, followed by thermal annealing at 700 °C during 5 h in air atmosphere. Some samples were irradiated with beta particles in the dose range from 8 up to 128 Gy. The sensitivity of Er doped samples was greater than the one of Ce-doped. In both cases, a 2 % mol of dopant concentration was used. The TL fading was between 19 % for Ce-doped samples, and 24 % for the Er-doped. The integrated TL increases as dose increases, with no saturation clues. The TL sensitivity of samples exhibited a loss in successive irradiation – readout cycles.
NaCl:Cu pellet-shaped phosphors were synthesized through a sintering process. Some samples were e... more NaCl:Cu pellet-shaped phosphors were synthesized through a sintering process. Some samples were exposed to beta irradiation in order to investigate their thermoluminescence properties and capabilities to be used in detecting and measuring ionizing radiation. The glow curves reveal at least four thermoluminescence peaks below 250°C, and a main one above 300°C when a 5°C/s heating rate is used. The lowest temperature peak vanishes in less than 3 min after irradiation, giving rise to an intense afterglow luminescence, potentially useful for in situ non-thermoluminescence dosimetry, and the next remains for about 3 h, but the high temperature one exhibits no important changes after that time. The thermoluminescence intensity increased as the radiation dose increased in the 0.417-25.0 Gy dose range. Because the position and the remarkable stability of the higher temperature peak, besides the strong afterglow produced by the fast decaying of the lower temperature peak, it is concluded that these phosphors are very suitable candidates to be used in both thermoluminescence and non thermoluminescence dosimetry of ionizing radiation, having advantages over monocrystals of similar composition. The synthesis route here followed can be reproduced in standard college laboratories, and thermoluminescence be measured in home-made systems, allowing design practices for interdisciplinary physics, chemistry electronics, and materials science students.
In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited ... more In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.
Advances in Materials Science and Engineering, 2016
In this work, we report the thermoluminescence (TL) properties of self-agglomerating CaSO4:Eu sam... more In this work, we report the thermoluminescence (TL) properties of self-agglomerating CaSO4:Eu samples obtained by an environmentally friendly coprecipitation technique. No binding material is needed to form solid CaSO4:Eu samples. Samples exposed to beta particle irradiation exhibit a TL maximum at 473.15 K when a 5 K/s heating rate is used, they are two times more sensitive than the TLD-100 commercial dosimeter, and their lower detection limit was determined to be less than 0.69 mGy. The computerized glow curve deconvolution carried out fitting the residual glow curves from McKeever method revealed that the whole glow curve is composed of four individual TL peaks with intermediate-order kinetics. The main peak order kinetics is b = 1.48. This result agrees with that computed using Chen’s formula.
SiO 2 coatings prepared by the sol-gel method containing various amounts of copper have been anne... more SiO 2 coatings prepared by the sol-gel method containing various amounts of copper have been annealed under two different atmospheres to produce colloidal copper based particles embedded in a SiO 2 matrix. The particle composition depended on: the amount of copper added to the stating solutions, the atmosphere in which the samples were annealed and the annealing temperature. The optical properties of the colloidal coatings were determined using the model proposed by Mie, using effective values for the optical constants of the colloidal particles.
In this work, the thermoluminescence (TL) characterization of pellet-shaped ZnO:Na phosphors synt... more In this work, the thermoluminescence (TL) characterization of pellet-shaped ZnO:Na phosphors synthesized through a controlled chemical reaction followed by thermal annealing at 900°C in air is reported. X-Ray diffraction patterns reveal ZnO hexagonal zincite structure for the samples, some of which were exposed to beta particle irradiation in the dose range from 0.08 to 2048 Gy in order to study their TL features. The synthesized ZnO:Na samples are more than 200 times more sensitive than ZnO samples synthesized by the same method, and present a 0.02 (1/50) sensitivity relative to the TLD-100 dosimeter.
We have sintered an alkali halide KClXBr1-X:Eu2+ ceramics phosphors. These KClXBr1-X:Eu2+ are con... more We have sintered an alkali halide KClXBr1-X:Eu2+ ceramics phosphors. These KClXBr1-X:Eu2+ are considered as promising selective ultraviolet dosimeter material and they exhibit situable optical characteristics for using in digital radiography and optical memory devices. In this work, the thermoluminescence glow cuves were analized as a function of composition x. We have found that for intermediate compositions, around x = 0.6,
Diamond thin films were deposited onto Si (100) substrates using liquid a solution of water and a... more Diamond thin films were deposited onto Si (100) substrates using liquid a solution of water and acetone, ethanol, methanol and commercial Tequila as precursors by the Pulsed Liquid Injection Chemical Vapor Deposition (PLICVD) technique. Temperature was varied from 550 °C to 850 °C. In this work we attempted to find a crystal diameter dependence on temperature and pressure from the experimental data. The goal in this work is to found a function that can be adjusted to the experimental data.
Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of 90 Sr beta particles.... more Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of 90 Sr beta particles. The diamond thin films have been synthesized from commercial Tequila as a precursor using Pulsed Liq uid Injection by the Chemical Vapor Deposition (PLICVD) technique reported recently. Thermolumines cence (TL) phenomena at these doses exhibit peak curve shift to higher temperatures (from 370 to 440 K) in the glow curve and the integrated TL curve show a linear behavior. Therefore, it has been considered that diamond thin films could be used as high doses dosimeters.
In this work, the thermoluminescence (TL) features of Sc 2 O 3 exposed to beta particle irradiati... more In this work, the thermoluminescence (TL) features of Sc 2 O 3 exposed to beta particle irradiation in the dose range from 0.08 to 150 Gy are reported. Characteristic glow curves exhibit two main TL maxima, located at 74 and 192°C when a 2°C/s heating rate is used. The TL response as a function of dose exhibits a linear behavior for doses below 70 Gy. We conclude that Sc 2 O 3 is a promising phosphor material for using as TL dosimeter.
APPC 2000 - Proceedings of the 8th Asia-Pacific Physics Conference, 2001
The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to... more The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to X -rays or beta radiation. The main thermoluminescence (TL) peaks were found around 370, 390 and 470 K. The 470 K highest intensity peak is considered to be the dosimetric peak due to its low fading and linear dose behavior. The main dosimetric peak is sharply decreased after illumination with UV light of a previously irradiated specimen. The PTTL is wavelength dependent and has been shown to peak in the 220 - 230 nm region and 650 nm in previously non irradiated and irradiated samples, respectively. The PTTL spectral response is always a broad band around 390 - 490 nm peaked at 425 nm, which is related to the well-known Eu2+ emission.
Alkali halides crystals have been the subject of intense research for an understanding of their r... more Alkali halides crystals have been the subject of intense research for an understanding of their radiation-induced defects and luminescence properties. They exhibit noteworthy thermoluminescence (TL) properties when exposed to ionising radiation. Currently, these materials are grown employing expensive and rather complicated techniques. In this work, the results on the TL properties of new alkali halides phosphors fabricated by a simple and inexpensive procedure are presented. The samples were made by mixing KCl, KBr and EuCl3 salts, and compressing them at a pressure of 3.2 x 10(7) Pa during 3 min, followed by sintering at 700 degrees C during 24 h under air atmosphere. The dosimetric response of the samples showed an increase with radiation dose in the 1.5-20.0 Gy dose range for beta and gamma radiation. The TL glow curves in sintered samples presented significant differences in their peak structures compared with monocrystalline samples, indicating that the nature of the trapping states and the recombination mechanisms may be different.
Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by puls... more Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by pulsed-liquid injection chemical vapour deposition at 850 degrees C. Some samples were exposed to beta particle irradiation in the dose range from 100 to 1600 Gy, and it was found that the thermoluminescence (TL) response is a linear function of dose. The glow curve displays two maxima centred at 170 and 350 degrees C, which does not shift when dose changes, indicating that first-order kinetics processes are involved. From the results, it is concluded that the new nanodiamond films are promising high-dose TL dosimeters.
Hot filament chemically vapor deposited (HFCVD) boron doped diamond films were grown on monocryst... more Hot filament chemically vapor deposited (HFCVD) boron doped diamond films were grown on monocrystalline silicon (111) doped with B/C ratios of 4000, 8000 and 12,000 ppm. Scanning electron micrographs show that the films are composed of well-faceted microcrystallites ranging in size from about 1 to 5 µm with no correlation with B/C concentration. The Raman spectra exhibit a sharp diamond band at 1332 cm-1 which shifts to lower wave numbers, broaden and decreases as the B/C ratio increases. An additional broad band is observed around 1200 cm −1. The beta irradiated diamond films exhibit thermoluminescence (TL) and optically stimulated luminescence (OSL) and the TL glow curves can be fitted well with four glow peaks. The kinetic parameters of these TL peaks as well as their intensities depend on B/C ratio. The OSL curves of the diamond films grown with 4000 and 8000 ppm of B/C exhibit standard decay behaviour for continuos stimulation with light of 470 nm. However, the OSL signal of the 12,000 ppm film increases initially with light stimulation, reaching a maximum to decay afterwards.
Pellet-shaped NaF:Eu 3+ phosphors were synthesized by sintering. When a 5 K/s heating rate was us... more Pellet-shaped NaF:Eu 3+ phosphors were synthesized by sintering. When a 5 K/s heating rate was used, the characteristic glow curves of beta particle irradiated samples exhibited two thermoluminescence (TL) maxima located at 401 K and 498 K, being the higher temperature maximum the most intense. A peak located between 473 and 523 K is considered to have a position very suitable to assure good thermal stability of the stored TL, so this phosphor is attractive for radiation dosimetry. Beta particle irradiated samples displayed a TL response that increases as the radiation dose increased in the 0.08 to 42.5 Gy dose range, with a linear behavior below 10 Gy followed by a sublinear one for higher doses. Under storage after irradiation, the TL maximum at 498 K displayed a remarkable stability, and the TL fading revealed that the maximum at 401 K is not a single peak.
The thermoluminescence (TL) response of samples obtained from human teeth exposed to beta irradia... more The thermoluminescence (TL) response of samples obtained from human teeth exposed to beta irradiation shows that the characteristic glow curves exhibit TL emission at high enough temperatures, which ensures thermal stability of the TL signal, and the TL increases as the dose increases from 0.25 up to 128 Gy, with linear behavior for doses below 32 Gy. The dose interval tested is of interest for clinical applications. Samples do not suffer damage due to heating if the TL readouts are performed from room temperature up to 300 °C. W This indicate that human teeth are promising phosphor materials for use in different TL and afterglow dosimetry applications.
Keywords: Thermoluminescence; Human Teeth; Dosimetry; β - Irradiated Human Teeth; Hydroxyapatite.
In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited ... more In this work, the synthesis of SrB4O7 through solid state reaction and its beta particle excited thermoluminescence (TL) are reported. The glow curves show maxima around 200 and 300 -considered suitable for TL dosimetry-, and a remarkable reproducibility in successive irradiation - TL readout cycles. The integrated TL exhibits a linear dependence upon the irradiation dose in the tested dose range (from 1.0 up to 8.0 Gy). The lower detection limit and the sensitivity relative to the TLD-100 dosimeter are 88 mGy and 0.49, respectively. From the results here presented, we conclude that SrB4O7 synthesized through solid state reaction can be considered a phosphor material interesting to develop TL dosimeters.
In this work, we report on the afterglow (AG) response characterization of commercially available... more In this work, we report on the afterglow (AG) response characterization of commercially available ZrO 2. Pellet shaped samples previously annealed in air at 1000 °C during 24 h were exposed to beta particle irradiation in the dose range from 0.5 up to 128 Gy and their AG decay curves recorded during 600 s after irradiation exposure. The characteristic glow curves of beta particle irradiated ZrO 2 show two maxima located around 80 °C and 150 °C. The first one rapidly vanishes at room temperature, giving rise to AG. The integrated AG signal increases as dose increases from 0.5 to 128 Gy, with a linear dependence from 0.5 up to ca. 32 Gy. Excellent reproducibility of the AG response was observed in 10 irradiation-AG readout cycles, showing that the studied ZrO 2 samples are reusable. The results here presented show that ZrO 2 is a promising material for use as a radiation dosimeter based on the AG phenomenon.
We report the photoconductance of ZnO thin films obtained from thermally treated ZnS films grown ... more We report the photoconductance of ZnO thin films obtained from thermally treated ZnS films grown by a chemical bath deposition method. The measurements of photo-conductance were performed in an atmosphere of air or nitrogen (N 2) at different temperatures between 300 K and 375 K. The augmented conductance after ultraviolet (UV) irradiation (330-380 nm) in air fades away slowly to its original value, whereas in a nitrogen atmosphere, a significant part of the augmented conductance remains. Measurements of electrical conductance as a function of temperature in N 2 or air, in the dark or the light, seem to indicate that the donor concentration is increased during the UV irradiation, suggesting that oxygen vacancies and interstitials are created. An alternative model for the photoconduction in ZnO is proposed in which the slow increase of conduction during irradiation is explained by an increase of donors instead of photoelectrons. In this model, the photoelectrons would only play a role in the mechanism of the creation of donors.
The thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phospho... more The thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phosphors are presented. Pellet-shaped samples were prepared by cool-pressing 74 μm size particle powder, followed by thermal annealing at 700 °C during 5 h in air atmosphere. Some samples were irradiated with beta particles in the dose range from 8 up to 128 Gy. The sensitivity of Er doped samples was greater than the one of Ce-doped. In both cases, a 2 % mol of dopant concentration was used. The TL fading was between 19 % for Ce-doped samples, and 24 % for the Er-doped. The integrated TL increases as dose increases, with no saturation clues. The TL sensitivity of samples exhibited a loss in successive irradiation – readout cycles.
NaCl:Cu pellet-shaped phosphors were synthesized through a sintering process. Some samples were e... more NaCl:Cu pellet-shaped phosphors were synthesized through a sintering process. Some samples were exposed to beta irradiation in order to investigate their thermoluminescence properties and capabilities to be used in detecting and measuring ionizing radiation. The glow curves reveal at least four thermoluminescence peaks below 250°C, and a main one above 300°C when a 5°C/s heating rate is used. The lowest temperature peak vanishes in less than 3 min after irradiation, giving rise to an intense afterglow luminescence, potentially useful for in situ non-thermoluminescence dosimetry, and the next remains for about 3 h, but the high temperature one exhibits no important changes after that time. The thermoluminescence intensity increased as the radiation dose increased in the 0.417-25.0 Gy dose range. Because the position and the remarkable stability of the higher temperature peak, besides the strong afterglow produced by the fast decaying of the lower temperature peak, it is concluded that these phosphors are very suitable candidates to be used in both thermoluminescence and non thermoluminescence dosimetry of ionizing radiation, having advantages over monocrystals of similar composition. The synthesis route here followed can be reproduced in standard college laboratories, and thermoluminescence be measured in home-made systems, allowing design practices for interdisciplinary physics, chemistry electronics, and materials science students.
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Papers by Rodolfo Bernal
Keywords: Thermoluminescence; Human Teeth; Dosimetry; β - Irradiated Human Teeth; Hydroxyapatite.
Keywords: Thermoluminescence; Human Teeth; Dosimetry; β - Irradiated Human Teeth; Hydroxyapatite.