A study of the kinetics of a high temperature thermoluminescence peak in annealed natural quartz
- Thomas, Sunil, Chithambo, Makaiko L
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110007 , vital:33213 , DOI: 10.1016/j.jlumin.2018.08.077
- Description: Thermoluminescence of a high temperature secondary glow-peak in natural quartz annealed at 900 °C is reported. The glow-curve of a sample irradiated to 10 Gy and measured at 1 °C/s shows three peaks; the main peak at 71 °C and two other weaker-intensity peaks at 125 °C and 177 °C. For reference, the peaks are labelled as I, II and III. This study is concerned with the secondary peak at 177 °C (peak III). The electron trap responsible for peak III is stable at ambient temperature as determined by monitoring the peak intensity after various delays between irradiation and measurement. The activation energy and frequency factor of the peak were estimated as ~1.24 eV and ~10¹² s⁻¹ respectively. The dose response of the peak in the range 1–300 Gy is sublinear. The influence of either partial heating or irradiation dose on the peak position suggest that the peak follows non-first-order kinetics.
- Full Text: false
- Date Issued: 2018
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110007 , vital:33213 , DOI: 10.1016/j.jlumin.2018.08.077
- Description: Thermoluminescence of a high temperature secondary glow-peak in natural quartz annealed at 900 °C is reported. The glow-curve of a sample irradiated to 10 Gy and measured at 1 °C/s shows three peaks; the main peak at 71 °C and two other weaker-intensity peaks at 125 °C and 177 °C. For reference, the peaks are labelled as I, II and III. This study is concerned with the secondary peak at 177 °C (peak III). The electron trap responsible for peak III is stable at ambient temperature as determined by monitoring the peak intensity after various delays between irradiation and measurement. The activation energy and frequency factor of the peak were estimated as ~1.24 eV and ~10¹² s⁻¹ respectively. The dose response of the peak in the range 1–300 Gy is sublinear. The influence of either partial heating or irradiation dose on the peak position suggest that the peak follows non-first-order kinetics.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of K-Mg-Al-Zn fluorophosphate glass
- Thomas, Sunil, Chithambo, Makaiko L
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124188 , vital:35574 , https://doi.org/10.1016/j.optmat.2016.12.035
- Description: The thermoluminescence of beta irradiated K-Mg-Al-Zn fluorophosphate glass is reported. A glow-curve corresponding to 10 Gy measured at 1 °C/s shows two peaks, a weaker-intensity one at 70 °C and a more prominent one at 235 °C, the subject of this report. The main peak was observed to fade with delay between irradiation and measurement and specifically, by 11% in 15 h. Its dose response is superlinear in the dose range 1–190 Gy although the change was linear for the initial 10 Gy. Regarding kinetic analysis, the activation energy of the higher temperature peak was evaluated as 1.31 eV and that of the lower temperature peak was found as 0.47 eV. It was also noted that the main peak is affected by thermal quenching with an activation energy for thermal quenching equal to 1.37 eV. It is proposed that the mechanism associated with the thermoluminescence in K-Mg-Al-Zn fluorophosphate glass is that electrons trapped by the metal cations are released during heating and then recombine with holes at oxygen sites.
- Full Text: false
- Date Issued: 2017
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124188 , vital:35574 , https://doi.org/10.1016/j.optmat.2016.12.035
- Description: The thermoluminescence of beta irradiated K-Mg-Al-Zn fluorophosphate glass is reported. A glow-curve corresponding to 10 Gy measured at 1 °C/s shows two peaks, a weaker-intensity one at 70 °C and a more prominent one at 235 °C, the subject of this report. The main peak was observed to fade with delay between irradiation and measurement and specifically, by 11% in 15 h. Its dose response is superlinear in the dose range 1–190 Gy although the change was linear for the initial 10 Gy. Regarding kinetic analysis, the activation energy of the higher temperature peak was evaluated as 1.31 eV and that of the lower temperature peak was found as 0.47 eV. It was also noted that the main peak is affected by thermal quenching with an activation energy for thermal quenching equal to 1.37 eV. It is proposed that the mechanism associated with the thermoluminescence in K-Mg-Al-Zn fluorophosphate glass is that electrons trapped by the metal cations are released during heating and then recombine with holes at oxygen sites.
- Full Text: false
- Date Issued: 2017
The influence of dopants on thermoluminescence of Sr2MgSi2O7
- Thomas, Sunil, Kalita, Jitumani M, Chithambo, Makaiko L, Ntwaeaborwa, Odireleng M
- Authors: Thomas, Sunil , Kalita, Jitumani M , Chithambo, Makaiko L , Ntwaeaborwa, Odireleng M
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105148 , vital:32469 , https://doi.org/10.1016/j.jlumin.2018.12.035
- Description: We report the influence of dopants on the thermoluminescence of Sr2MgSi2O7. Samples studied comprise undoped Sr2MgSi2O7 and doped versions, namely, Sr2MgSi2O7:Dy3+, Sr2MgSi2O7:Eu3+, Sr2MgSi2O7:Tb3+ and Sr2MgSi2O7:Tb3+,Eu3+ phosphors. All samples show a broad glow peak near 60 °C when measured at 1 °C/s after irradiation to 10 Gy. The peak changes with partial heating, irradiation and fades between irradiation and measurement in a manner expected of a composite one. The behaviour is used to exemplify the analysis of a composite peak on the basis that particular features reflect those of the dominant component.
- Full Text: false
- Date Issued: 2019
- Authors: Thomas, Sunil , Kalita, Jitumani M , Chithambo, Makaiko L , Ntwaeaborwa, Odireleng M
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105148 , vital:32469 , https://doi.org/10.1016/j.jlumin.2018.12.035
- Description: We report the influence of dopants on the thermoluminescence of Sr2MgSi2O7. Samples studied comprise undoped Sr2MgSi2O7 and doped versions, namely, Sr2MgSi2O7:Dy3+, Sr2MgSi2O7:Eu3+, Sr2MgSi2O7:Tb3+ and Sr2MgSi2O7:Tb3+,Eu3+ phosphors. All samples show a broad glow peak near 60 °C when measured at 1 °C/s after irradiation to 10 Gy. The peak changes with partial heating, irradiation and fades between irradiation and measurement in a manner expected of a composite one. The behaviour is used to exemplify the analysis of a composite peak on the basis that particular features reflect those of the dominant component.
- Full Text: false
- Date Issued: 2019
General features and kinetic analysis of thermoluminescence from annealed natural quartz
- Thomas, Sunil, Chithambo, Makaiko L
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112885 , vital:33670 , https://doi.org/10.1016/j.jlumin.2018.02.003
- Description: The aim of this study is to explore the thermoluminescence properties of beta irradiated natural quartz annealed at 900 °C, that is, beyond its second phase inversion temperature of 867 °C. The sample was annealed to improve its sensitivity and to deplete any residual charge from electron traps. The glow-curve corresponding to 10 Gy shows three peaks when measured at 1 °C/s; a dominant one at 71 °C, the subject of this report, and two other ones at 125 and 177 °C. The dose response of the main peak was studied in the range 1–300 Gy. The activation energy of the main glow-peak was evaluated as ~1 eV. Kinetic analyses using various methods show that the main glow-peak follows first order kinetics.
- Full Text: false
- Date Issued: 2018
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112885 , vital:33670 , https://doi.org/10.1016/j.jlumin.2018.02.003
- Description: The aim of this study is to explore the thermoluminescence properties of beta irradiated natural quartz annealed at 900 °C, that is, beyond its second phase inversion temperature of 867 °C. The sample was annealed to improve its sensitivity and to deplete any residual charge from electron traps. The glow-curve corresponding to 10 Gy shows three peaks when measured at 1 °C/s; a dominant one at 71 °C, the subject of this report, and two other ones at 125 and 177 °C. The dose response of the main peak was studied in the range 1–300 Gy. The activation energy of the main glow-peak was evaluated as ~1 eV. Kinetic analyses using various methods show that the main glow-peak follows first order kinetics.
- Full Text: false
- Date Issued: 2018
Kinetic analysis and general features of thermoluminescence of B2O3-Li2O-ZnF2 glass
- Thomas, Sunil, Chithambo, Makaiko L
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116154 , vital:34324 , https://doi.org/10.1016/j.radmeas.2017.03.038
- Description: The intention of this study is to explore the thermoluminescence of beta irradiated B2O3-Li2O-ZnF2 glass. The glow-curve corresponding to 200 Gy shows three peaks; two weak-intensity peaks at 60 and 243 °C and a more prominent one at 118 °C, when measured at 1 °C/s. The dose response of the main peak at 118 °C was found to be sublinear in the range 200–1000 Gy. Regarding the kinetic analysis of the main peak, the activation energy of the corresponding electron trap was evaluated as 0.96 eV and the frequency factor as ∼1011 s−1. It is proposed that the thermoluminescence in B2O3-Li2O-ZnF2 glass is due to recombination of electrons, thermally released from Zn+ ionic defect sites, with the holes at boron-oxygen hole centres.
- Full Text: false
- Date Issued: 2017
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116154 , vital:34324 , https://doi.org/10.1016/j.radmeas.2017.03.038
- Description: The intention of this study is to explore the thermoluminescence of beta irradiated B2O3-Li2O-ZnF2 glass. The glow-curve corresponding to 200 Gy shows three peaks; two weak-intensity peaks at 60 and 243 °C and a more prominent one at 118 °C, when measured at 1 °C/s. The dose response of the main peak at 118 °C was found to be sublinear in the range 200–1000 Gy. Regarding the kinetic analysis of the main peak, the activation energy of the corresponding electron trap was evaluated as 0.96 eV and the frequency factor as ∼1011 s−1. It is proposed that the thermoluminescence in B2O3-Li2O-ZnF2 glass is due to recombination of electrons, thermally released from Zn+ ionic defect sites, with the holes at boron-oxygen hole centres.
- Full Text: false
- Date Issued: 2017
Characteristics of the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass
- Thomas, Sunil, Chithambo, Makaiko L
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109979 , vital:33211 , https://doi.org/10.1016/j.radmeas.2018.06.005
- Description: We report the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass. A glow-curve measured at 1 °C/s after beta irradiation to 10 Gy shows two peaks; a broad high intensity one at 214.0 ± 0.4 °C and a weaker intensity peak at 75.2 ± 0.8 °C. The dependence of peak position on partial heating as well as on irradiation suggest that the main peak at 214 °C is a combination of several overlapping peaks. The activation energy of the different components of the main peak, calculated using the initial-rise method, differ showing that the components are distinct. The reproducibility, fading and dose response were examined by considering the dominant component of the main peak. The intensity of the peak changes with heating rate in a manner consistent with thermal quenching.
- Full Text: false
- Date Issued: 2018
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109979 , vital:33211 , https://doi.org/10.1016/j.radmeas.2018.06.005
- Description: We report the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass. A glow-curve measured at 1 °C/s after beta irradiation to 10 Gy shows two peaks; a broad high intensity one at 214.0 ± 0.4 °C and a weaker intensity peak at 75.2 ± 0.8 °C. The dependence of peak position on partial heating as well as on irradiation suggest that the main peak at 214 °C is a combination of several overlapping peaks. The activation energy of the different components of the main peak, calculated using the initial-rise method, differ showing that the components are distinct. The reproducibility, fading and dose response were examined by considering the dominant component of the main peak. The intensity of the peak changes with heating rate in a manner consistent with thermal quenching.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of the persistent-luminescence phosphor, BaAl2O4: a stuffed tridymite
- Pandey, A, Chithambo, Makaiko L
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of kunzite: a study of kinetic processes and dosimetry characteristics
- Ogundare, F O, Alatishe, M A, Chithambo, Makaiko L, Costin, G
- Authors: Ogundare, F O , Alatishe, M A , Chithambo, Makaiko L , Costin, G
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124701 , vital:35650 , https://doi.org/10.1016/j.nimb.2016.02.059
- Description: Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer.
- Full Text: false
- Date Issued: 2016
- Authors: Ogundare, F O , Alatishe, M A , Chithambo, Makaiko L , Costin, G
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124701 , vital:35650 , https://doi.org/10.1016/j.nimb.2016.02.059
- Description: Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer.
- Full Text: false
- Date Issued: 2016
Factors influencing the shape of CW-OSL signal obtained by stimulation of very deep traps in carbon-doped aluminium oxide: an experimental study
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115493 , vital:34149 , https://doi.org/10.1016/j.jlumin.2017.07.016
- Description: The optically stimulated luminescence from carbon-doped aluminium oxide (α-Al2O3:C) displays a peak with time under certain measurement conditions. In this paper, we present factors that influence the peak-like shape of continuous-wave optically stimulated luminescence (CW-OSL) signal. The report is based on the experimental study of OSL signals obtained by stimulation of very deep traps in α-Al2O3:C. Methods exploiting post-irradiation annealing, variable dose and temperature dependent OSL measurements were used in the investigation. It is found that the rising part of the CW-OSL peak is obtained when the rate of retrapping at the most optically active trap (main trap) exceeds the rate of direct radiative recombination following optical release of charges from all optically active traps. This is possible if, during optical stimulation, the primary trap responsible for OSL i.e. the main trap, is substantially unoccupied and the very deep, donor traps are substantially filled up. The rate of charge retrapping itself is deduced to depend on the occupancy of the acceptor traps i.e. shallow, main and secondary traps; concentration of charge carriers in the very deep, donor traps; the post-irradiation annealing temperature and the temperature at which the OSL is measured.
- Full Text: false
- Date Issued: 2017
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115493 , vital:34149 , https://doi.org/10.1016/j.jlumin.2017.07.016
- Description: The optically stimulated luminescence from carbon-doped aluminium oxide (α-Al2O3:C) displays a peak with time under certain measurement conditions. In this paper, we present factors that influence the peak-like shape of continuous-wave optically stimulated luminescence (CW-OSL) signal. The report is based on the experimental study of OSL signals obtained by stimulation of very deep traps in α-Al2O3:C. Methods exploiting post-irradiation annealing, variable dose and temperature dependent OSL measurements were used in the investigation. It is found that the rising part of the CW-OSL peak is obtained when the rate of retrapping at the most optically active trap (main trap) exceeds the rate of direct radiative recombination following optical release of charges from all optically active traps. This is possible if, during optical stimulation, the primary trap responsible for OSL i.e. the main trap, is substantially unoccupied and the very deep, donor traps are substantially filled up. The rate of charge retrapping itself is deduced to depend on the occupancy of the acceptor traps i.e. shallow, main and secondary traps; concentration of charge carriers in the very deep, donor traps; the post-irradiation annealing temperature and the temperature at which the OSL is measured.
- Full Text: false
- Date Issued: 2017
The influence of radiation-induced defects on thermoluminescence and optically stimulated luminescence of α-Al2O3: C
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119818 , vital:34786 , https://doi.org/10.1016/j.nimb.2017.02.077
- Description: It is known that when α-Al2O3:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al2O3:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.
- Full Text: false
- Date Issued: 2017
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119818 , vital:34786 , https://doi.org/10.1016/j.nimb.2017.02.077
- Description: It is known that when α-Al2O3:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al2O3:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.
- Full Text: false
- Date Issued: 2017
Spectral study of radioluminescence in carbon-doped aluminium oxide
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110067 , vital:33220 , https://doi.org/10.1016/j.radmeas.2018.06.026
- Description: The spectral emission study of the radioluminescence (RL) measured from carbon-doped aluminium oxide (α-Al2O3:C) at various temperatures between 30 and 300∘C is reported. The energy-resolved RL emission spectra measured at room temperature show seven gaussian emission bands centred at 1.75, 1.79, 1.85, 2.22, 2.96, 3.72 and 4.44 eV. The 2.96-eV emission, associated with F-centres, is the primary RL emission whereas the narrow (R-line) emission centred at 1.79 eV, associated with Cr3+ impurity ions, is the most intense secondary emission. However, the intensity of 1.79-eV emission decreases with repeated RL measurements. The central emission energy for F-centres is constant throughout the temperature range of investigation. The full width at half maximum (FWHM) for the F-centre emission band increases with temperature whereas the F-centre peak intensity exhibits thermal quenching behaviour at temperatures above 160∘C. On the other hand, the emission energy for the R-line emission of Cr3+ is constant for temperatures between 30 and 160∘C, whereas its peak intensity generally decreases with temperature. F-centres experience strong-coupling in their crystallographic sites with estimated electron-lattice coupling parameters of S = 5.0 ± 0.9, Ep = 0.079 ± 0.008 eV and ν = 1.91 × 1013 Hz where S, Ep and ν are the Huang-Rhys factor, the phonon energy and the phonon frequency, respectively. The RL spectra recorded while ramping the temperature of a sample at a constant rate have been compared against conventional TL spectra.
- Full Text: false
- Date Issued: 2018
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110067 , vital:33220 , https://doi.org/10.1016/j.radmeas.2018.06.026
- Description: The spectral emission study of the radioluminescence (RL) measured from carbon-doped aluminium oxide (α-Al2O3:C) at various temperatures between 30 and 300∘C is reported. The energy-resolved RL emission spectra measured at room temperature show seven gaussian emission bands centred at 1.75, 1.79, 1.85, 2.22, 2.96, 3.72 and 4.44 eV. The 2.96-eV emission, associated with F-centres, is the primary RL emission whereas the narrow (R-line) emission centred at 1.79 eV, associated with Cr3+ impurity ions, is the most intense secondary emission. However, the intensity of 1.79-eV emission decreases with repeated RL measurements. The central emission energy for F-centres is constant throughout the temperature range of investigation. The full width at half maximum (FWHM) for the F-centre emission band increases with temperature whereas the F-centre peak intensity exhibits thermal quenching behaviour at temperatures above 160∘C. On the other hand, the emission energy for the R-line emission of Cr3+ is constant for temperatures between 30 and 160∘C, whereas its peak intensity generally decreases with temperature. F-centres experience strong-coupling in their crystallographic sites with estimated electron-lattice coupling parameters of S = 5.0 ± 0.9, Ep = 0.079 ± 0.008 eV and ν = 1.91 × 1013 Hz where S, Ep and ν are the Huang-Rhys factor, the phonon energy and the phonon frequency, respectively. The RL spectra recorded while ramping the temperature of a sample at a constant rate have been compared against conventional TL spectra.
- Full Text: false
- Date Issued: 2018
On luminescence stimulated from deep traps using thermally-assisted time-resolved optical stimulation in α-Al2O3: C
- Nyirenda, Angel N, Chithambo, Makaiko L, Polymeris, G S
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L , Polymeris, G S
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124627 , vital:35639 , https://doi.org/10.1016/j.radmeas.2016.01.016
- Description: We report a study of charge transfer mechanisms of electrons stimulated optically from very deep traps, also known as donor traps, in α-Al2O3:C. The investigations were carried out using thermally-assisted time-resolved optical stimulation, thermoluminescence and by way of residual thermoluminescence from the main electron trap. When the charges are optically stimulated from the deep traps, they are redistributed via the conduction band to the main electron trap and the shallow trap from where they are optically or thermally released for recombination at luminescence centres. The luminescence is strongly quenched at high measurement temperature as evident by very short luminescence lifetimes at these temperatures. The main peak due to residual thermoluminescence is located at a higher temperature than the conventional main peak.
- Full Text: false
- Date Issued: 2016
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L , Polymeris, G S
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124627 , vital:35639 , https://doi.org/10.1016/j.radmeas.2016.01.016
- Description: We report a study of charge transfer mechanisms of electrons stimulated optically from very deep traps, also known as donor traps, in α-Al2O3:C. The investigations were carried out using thermally-assisted time-resolved optical stimulation, thermoluminescence and by way of residual thermoluminescence from the main electron trap. When the charges are optically stimulated from the deep traps, they are redistributed via the conduction band to the main electron trap and the shallow trap from where they are optically or thermally released for recombination at luminescence centres. The luminescence is strongly quenched at high measurement temperature as evident by very short luminescence lifetimes at these temperatures. The main peak due to residual thermoluminescence is located at a higher temperature than the conventional main peak.
- Full Text: false
- Date Issued: 2016
Influence of argon-implantation on conventional and phototransferred thermoluminescence of synthetic quartz
- Nsengiyumva, S, Chithambo, Makaiko L, Pichon, L
- Authors: Nsengiyumva, S , Chithambo, Makaiko L , Pichon, L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124732 , vital:35656 , DOI: 10.1080/10420150.2016.1194412
- Description: Conventional and phototransferred thermoluminescence of crystalline synthetic quartz implanted with 70 keV Ar ions at fluences in the range 1 × 1014–5 × 1015 ions/cm2 is reported. The glow curves, recorded at 5°C/s from beta-irradiated samples of similar mass, show a prominent peak between 100°C and 120°C. The thermoluminescence intensity of all implanted samples was greater than that of the unimplanted one. The increase in sensitivity is attributed to a corresponding increase in the concentration of point defects, as a result of the implantation, which act as electron traps or recombination centres. Kinetic analysis carried out using the peak shape, whole glow-peak and curve-fitting methods produced values of the activation energy, frequency factor and order of kinetics that are generally independent of implantation fluence. This result suggests that implantation did not necessarily affect the nature of the electron traps. With respect to phototransferred thermoluminescence, it was observed that it only appeared in the sample implanted at the highest fluence of 5 × 1015 ions/cm2. This may be so because the concentration of deep traps produced as a result of implantation at low fluence is too low to give rise to phototransferred thermoluminescence. The intensity of the phototransferred thermoluminescence goes through a peak with illumination time. We attribute this behaviour to the relative concentration of holes at recombination centres and phototransferred electrons at shallow traps.
- Full Text: false
- Date Issued: 2016
- Authors: Nsengiyumva, S , Chithambo, Makaiko L , Pichon, L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124732 , vital:35656 , DOI: 10.1080/10420150.2016.1194412
- Description: Conventional and phototransferred thermoluminescence of crystalline synthetic quartz implanted with 70 keV Ar ions at fluences in the range 1 × 1014–5 × 1015 ions/cm2 is reported. The glow curves, recorded at 5°C/s from beta-irradiated samples of similar mass, show a prominent peak between 100°C and 120°C. The thermoluminescence intensity of all implanted samples was greater than that of the unimplanted one. The increase in sensitivity is attributed to a corresponding increase in the concentration of point defects, as a result of the implantation, which act as electron traps or recombination centres. Kinetic analysis carried out using the peak shape, whole glow-peak and curve-fitting methods produced values of the activation energy, frequency factor and order of kinetics that are generally independent of implantation fluence. This result suggests that implantation did not necessarily affect the nature of the electron traps. With respect to phototransferred thermoluminescence, it was observed that it only appeared in the sample implanted at the highest fluence of 5 × 1015 ions/cm2. This may be so because the concentration of deep traps produced as a result of implantation at low fluence is too low to give rise to phototransferred thermoluminescence. The intensity of the phototransferred thermoluminescence goes through a peak with illumination time. We attribute this behaviour to the relative concentration of holes at recombination centres and phototransferred electrons at shallow traps.
- Full Text: false
- Date Issued: 2016
Photoluminescence and thermoluminescence properties of BaGa2O4
- Noto, L L, Poelman, D, Orante-Barrón, V R, Swart, H C, Mathevula, Langutani E, Nyenge, R, Chithambo, Makaiko L, Mothudi, B M, Dhlamini, M S
- Authors: Noto, L L , Poelman, D , Orante-Barrón, V R , Swart, H C , Mathevula, Langutani E , Nyenge, R , Chithambo, Makaiko L , Mothudi, B M , Dhlamini, M S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116037 , vital:34292 , https://doi.org/10.1016/j.physb.2017.07.059
- Description: Rare–Earth free luminescent materials are fast becoming important as the cost of rare earth ions gradually increases. In this work, a Rare–Earth free BaGa2O4 luminescent compound was prepared by solid state chemical reaction, which was confirmed to have a single phase by X-ray Diffraction. The Backscattered Electron image and Energy Dispersive X-ray spectroscopy maps confirmed irregular particle and homogeneous compound formation, respectively. The Photoluminescence spectrum displayed broad emission between 350 to 650 nm, which was deconvoluted into two components. The photoluminescence excitation peak was positioned at 254 nm, which corresponds with the band-to-band position observed from the diffuse reflectance spectrum. The band gap was extrapolated to 4.65 ± 0.02 eV using the Kubelka-Munk model. The preliminary thermoluminescence results indicated that the kinetics involved were neither of first nor second order. Additionally, the activation energy of the electrons within the trap centres was approximated to 0.61 ± 0.01 eV using the Initial Rise model.
- Full Text: false
- Date Issued: 2018
- Authors: Noto, L L , Poelman, D , Orante-Barrón, V R , Swart, H C , Mathevula, Langutani E , Nyenge, R , Chithambo, Makaiko L , Mothudi, B M , Dhlamini, M S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116037 , vital:34292 , https://doi.org/10.1016/j.physb.2017.07.059
- Description: Rare–Earth free luminescent materials are fast becoming important as the cost of rare earth ions gradually increases. In this work, a Rare–Earth free BaGa2O4 luminescent compound was prepared by solid state chemical reaction, which was confirmed to have a single phase by X-ray Diffraction. The Backscattered Electron image and Energy Dispersive X-ray spectroscopy maps confirmed irregular particle and homogeneous compound formation, respectively. The Photoluminescence spectrum displayed broad emission between 350 to 650 nm, which was deconvoluted into two components. The photoluminescence excitation peak was positioned at 254 nm, which corresponds with the band-to-band position observed from the diffuse reflectance spectrum. The band gap was extrapolated to 4.65 ± 0.02 eV using the Kubelka-Munk model. The preliminary thermoluminescence results indicated that the kinetics involved were neither of first nor second order. Additionally, the activation energy of the electrons within the trap centres was approximated to 0.61 ± 0.01 eV using the Initial Rise model.
- Full Text: false
- Date Issued: 2018
Structural and optical properties of sol-gel derived α-Fe2O3 nanoparticles
- Mathevula, Langutani E, Noto, L L, Mothudi, Bakang M, Chithambo, Makaiko L, Dhlamini, M S
- Authors: Mathevula, Langutani E , Noto, L L , Mothudi, Bakang M , Chithambo, Makaiko L , Dhlamini, M S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115467 , vital:34145 , DOI: 10.1016/j.jlumin.2017.07.055
- Description: α-Fe2O3 nanoparticles of crystallite size between 3.9 and 9.5 nm were synthesized by a simple sol-gel method using iron (III) nitrate nonahydrate (Fe(NO3)3·9H2O) as a precursor. Polyvinyl alcohol (PVA) was added as a capping agent to avoid agglomeration of the nanoparticles. A single pure phase was obtained when the sample was annealed at 300 °C and 600 °C. The purity was further confirmed with the Fourier Transform Infrared Spectroscopy. The energy band gap of the materials was extrapolated from the Kubelka-Munk relation and it ranges between 1.8 and 2.3 eV. The Photoluminescence of the 3 samples shows a broad emission spectrum centered at about 422 nm when excited by a 336 nm lamp. The emission peaks intensities increased with an increase in the annealing temperature, accept for the 576 nm peak, which was quenched as the temperature increased from 300 °C to 600 °C. The thermoluminescence glow curves were carried out at different heating rates and the samples were exposed to different beta particle doses (82–1315 Gy). The activation energy of the trapped electrons was determined.
- Full Text: false
- Date Issued: 2017
- Authors: Mathevula, Langutani E , Noto, L L , Mothudi, Bakang M , Chithambo, Makaiko L , Dhlamini, M S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115467 , vital:34145 , DOI: 10.1016/j.jlumin.2017.07.055
- Description: α-Fe2O3 nanoparticles of crystallite size between 3.9 and 9.5 nm were synthesized by a simple sol-gel method using iron (III) nitrate nonahydrate (Fe(NO3)3·9H2O) as a precursor. Polyvinyl alcohol (PVA) was added as a capping agent to avoid agglomeration of the nanoparticles. A single pure phase was obtained when the sample was annealed at 300 °C and 600 °C. The purity was further confirmed with the Fourier Transform Infrared Spectroscopy. The energy band gap of the materials was extrapolated from the Kubelka-Munk relation and it ranges between 1.8 and 2.3 eV. The Photoluminescence of the 3 samples shows a broad emission spectrum centered at about 422 nm when excited by a 336 nm lamp. The emission peaks intensities increased with an increase in the annealing temperature, accept for the 576 nm peak, which was quenched as the temperature increased from 300 °C to 600 °C. The thermoluminescence glow curves were carried out at different heating rates and the samples were exposed to different beta particle doses (82–1315 Gy). The activation energy of the trapped electrons was determined.
- Full Text: false
- Date Issued: 2017
Phototransferred thermoluminescence and thermally-assisted optically stimulated luminescence dosimetry using α-Al2O3:C,Mg annealed at 1200°C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105422 , vital:32511 , https://doi.org/10.1016/j.jlumin.2018.08.085
- Description: We report phototransferred thermoluminescence (PTTL) and thermally-assisted optically stimulated luminescence (TA-OSL) of α-Al2O3:C,Mg annealed at 1200 °C. PTTL is TL measured from an irradiated phosphor after its exposure to light. The other theme of this study, TA-OSL is the additional amount of luminescence optically stimulated from a sample over and above the amount that would be measured at room temperature. A sample irradiated to 10 Gy and preheated to 230 °C at 1 °C/s followed by illumination by 470 nm blue light produced four PTTL peaks at 53, 80, 102 and 173 °C. The PTTL peaks occur at the same positions as the corresponding conventional TL peaks. Their kinetic parameters are also similar. The intensity of the PTTL peaks increased with duration of illumination to a maximum within 200 s for doses between 1 Gy and 10 Gy. The dose response of each of the PTTL peaks at 80, 102 and 173 °C is linear within 1–15 Gy. The rate of fading is low and the peaks are reproducible. When the irradiated sample is optically stimulated at temperatures between 30 °C and 300 °C, after preheating to 500 °C, the intensity of its TA-OSL goes through a peak with temperature at 200 °C. Using the rising edge of the plot, activation energy of thermal assistance for a deep electron trap was estimated as (0.21 ± 0.02) eV. The TA-OSL dose response is sublinear from 10–250 Gy and saturates thereafter. The PTTL and TA-OSL analyses signify that the concentration of deep traps in α-Al2O3:C,Mg increased after annealing at 1200 °C. As a result, the sample produced better PTTL and TA-OSL response than when annealed at lower temperature.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105422 , vital:32511 , https://doi.org/10.1016/j.jlumin.2018.08.085
- Description: We report phototransferred thermoluminescence (PTTL) and thermally-assisted optically stimulated luminescence (TA-OSL) of α-Al2O3:C,Mg annealed at 1200 °C. PTTL is TL measured from an irradiated phosphor after its exposure to light. The other theme of this study, TA-OSL is the additional amount of luminescence optically stimulated from a sample over and above the amount that would be measured at room temperature. A sample irradiated to 10 Gy and preheated to 230 °C at 1 °C/s followed by illumination by 470 nm blue light produced four PTTL peaks at 53, 80, 102 and 173 °C. The PTTL peaks occur at the same positions as the corresponding conventional TL peaks. Their kinetic parameters are also similar. The intensity of the PTTL peaks increased with duration of illumination to a maximum within 200 s for doses between 1 Gy and 10 Gy. The dose response of each of the PTTL peaks at 80, 102 and 173 °C is linear within 1–15 Gy. The rate of fading is low and the peaks are reproducible. When the irradiated sample is optically stimulated at temperatures between 30 °C and 300 °C, after preheating to 500 °C, the intensity of its TA-OSL goes through a peak with temperature at 200 °C. Using the rising edge of the plot, activation energy of thermal assistance for a deep electron trap was estimated as (0.21 ± 0.02) eV. The TA-OSL dose response is sublinear from 10–250 Gy and saturates thereafter. The PTTL and TA-OSL analyses signify that the concentration of deep traps in α-Al2O3:C,Mg increased after annealing at 1200 °C. As a result, the sample produced better PTTL and TA-OSL response than when annealed at lower temperature.
- Full Text: false
- Date Issued: 2018
The effect of annealing and beta irradiation on thermoluminescence spectra of α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112875 , vital:33669 , https://doi.org/10.1016/j.jlumin.2017.12.036
- Description: The effect of annealing on thermoluminescence spectra of beta irradiated α-Al2O3:C,Mg has been studied. Measurements were made on an un-annealed sample and samples annealed at 600, 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy shows a high intensity peak at 163 °C and six secondary peaks of weaker intensity at 43, 73, 195, 280, 329 and 370 °C. When the samples are annealed at 700 or 900 °C, an additional secondary peak appears at 100 °C. The thermoluminescence spectrum of an un-annealed sample measured at 1 °C/s between 300 and 700 nm shows the main emission band at ~ 410 nm and subsidiary emission bands at ~ 325 and 485 nm. The emission from samples annealed at 700 and 900 °C show similar bands except for a decrease in intensity of the emission at 485 nm. The emission bands at 325, 410 and 485 nm are attributed to F+, F and F22+(2Mg) -centres respectively. The decrease of the emission band at 485 nm is deduced to be due to the destruction of the F22+(2Mg) centre at 700 °C. The emission bands are unaffected by irradiation dose between 10 and 320 Gy. However, when the sample is annealed at or beyond 700 °C, any effects on the F+ and F centres emission can be easier distinguished particularly for doses greater than 10 Gy.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112875 , vital:33669 , https://doi.org/10.1016/j.jlumin.2017.12.036
- Description: The effect of annealing on thermoluminescence spectra of beta irradiated α-Al2O3:C,Mg has been studied. Measurements were made on an un-annealed sample and samples annealed at 600, 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy shows a high intensity peak at 163 °C and six secondary peaks of weaker intensity at 43, 73, 195, 280, 329 and 370 °C. When the samples are annealed at 700 or 900 °C, an additional secondary peak appears at 100 °C. The thermoluminescence spectrum of an un-annealed sample measured at 1 °C/s between 300 and 700 nm shows the main emission band at ~ 410 nm and subsidiary emission bands at ~ 325 and 485 nm. The emission from samples annealed at 700 and 900 °C show similar bands except for a decrease in intensity of the emission at 485 nm. The emission bands at 325, 410 and 485 nm are attributed to F+, F and F22+(2Mg) -centres respectively. The decrease of the emission band at 485 nm is deduced to be due to the destruction of the F22+(2Mg) centre at 700 °C. The emission bands are unaffected by irradiation dose between 10 and 320 Gy. However, when the sample is annealed at or beyond 700 °C, any effects on the F+ and F centres emission can be easier distinguished particularly for doses greater than 10 Gy.
- Full Text: false
- Date Issued: 2018
Thermally and optically stimulated luminescence of natural red and blue corundum (Al2O3)
- Kalita, Jitumani M, Thomas, Sunil, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Thomas, Sunil , Chithambo, Makaiko L
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105177 , vital:32472 , https://doi.org/10.1016/j.jlumin.2018.09.058
- Description: We report the thermoluminescence (TL) and optically stimulated luminescence (OSL) of natural corundum (Al2O3) of two varieties; one red and the other blue. X-ray fluorescence spectroscopy of the samples show that the concentration of Al2O3 in the red corundum is 43.05% and 46.87% in the blue corundum. TL measurements carried out on un-annealed samples and samples annealed at 700 °C, 900 °C and 1200 °C show that the TL sensitivity increases with annealing. The sensitivity of the red corundum reaches a maximum after annealing at 900 °C whereas that of the blue corundum increases with annealing up to the maximum annealing temperature of 1200 °C used in this study. Both samples have a complex glow curve between 30 °C and 500 °C. The composite nature of the glow curves is deduced to be due to a continuum in the trap distribution in the crystal. The activation energy of the traps vary between 0.70 eV and 1.15 eV. The dose response of the red corundum under TL is linear within 100‒1000 Gy whereas that of the blue corundum is superlinear for the same dose range. The TL of both samples is reproducible but the signal fades with time between irradiation and measurement. Both samples produce OSL under 470 nm blue light stimulation. The dose response of the OSL is superlinear within 100‒1000 Gy. It is found that the samples also produce thermally-assisted OSL (TA-OSL) at elevated temperature. The TA-OSL intensity of the red corundum increases with dose up to 400 Gy and saturates thereafter. On the other hand, the intensity of the blue corundum increases consistently with dose from 100 Gy to 1000 Gy.
- Full Text: false
- Date Issued: 2019
- Authors: Kalita, Jitumani M , Thomas, Sunil , Chithambo, Makaiko L
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105177 , vital:32472 , https://doi.org/10.1016/j.jlumin.2018.09.058
- Description: We report the thermoluminescence (TL) and optically stimulated luminescence (OSL) of natural corundum (Al2O3) of two varieties; one red and the other blue. X-ray fluorescence spectroscopy of the samples show that the concentration of Al2O3 in the red corundum is 43.05% and 46.87% in the blue corundum. TL measurements carried out on un-annealed samples and samples annealed at 700 °C, 900 °C and 1200 °C show that the TL sensitivity increases with annealing. The sensitivity of the red corundum reaches a maximum after annealing at 900 °C whereas that of the blue corundum increases with annealing up to the maximum annealing temperature of 1200 °C used in this study. Both samples have a complex glow curve between 30 °C and 500 °C. The composite nature of the glow curves is deduced to be due to a continuum in the trap distribution in the crystal. The activation energy of the traps vary between 0.70 eV and 1.15 eV. The dose response of the red corundum under TL is linear within 100‒1000 Gy whereas that of the blue corundum is superlinear for the same dose range. The TL of both samples is reproducible but the signal fades with time between irradiation and measurement. Both samples produce OSL under 470 nm blue light stimulation. The dose response of the OSL is superlinear within 100‒1000 Gy. It is found that the samples also produce thermally-assisted OSL (TA-OSL) at elevated temperature. The TA-OSL intensity of the red corundum increases with dose up to 400 Gy and saturates thereafter. On the other hand, the intensity of the blue corundum increases consistently with dose from 100 Gy to 1000 Gy.
- Full Text: false
- Date Issued: 2019
Comprehensive kinetic analysis of thermoluminescence peaks of α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116142 , vital:34323 , https://doi.org/10.1016/j.jlumin.2017.01.003
- Description: A comprehensive kinetic analysis of the glow peaks in α-Al2O3:C,Mg is reported. A thermoluminescence glow curve measured at 1 °C/s after beta irradiation to 1 Gy shows a high intensity peak hereafter referred to as the main peak at 161 °C and six lower intensity secondary peaks at 42, 72, 193, 279, 330, 370 °C respectively. For ease of reference, the secondary peaks are labelled as I, II, IV, V, VI and VII respectively and the main peak denoted peak III. Kinetic analysis of the glow peaks has been carried out using the initial rise, whole glow peak, peak shape, variable heating rate and glow curve deconvolution methods as well as by way of phosphorescence. Using Tm-Tstop, Tm-dose and phosphorescence analyses, the order of kinetics of the peaks has been evaluated as first order. Analysis by the peak shape, whole glow peak and deconvolution methods produce the same conclusion. The activation energy of peaks I through VII are calculated as ~0.83, 0.96, 1.37, 1.20, 1.15, 1.61 and 1.94 eV respectively. The frequency factors for all the peaks are of the order of 109 to 1014 s−1. The question of thermal quenching affecting the peaks was considered. The peaks III, IV and V, the only ones that could be conveniently studied in this regard, were found to be affected by thermal quenching. The activation energy for thermal quenching was calculated for peak III as 0.96±0.03 eV, for peak VI as 0.95±0.07 eV and for peak V as 1.26±0.08 eV. The thermal quenching phenomenon has been discussed with reference to F+ and F centres. An energy band model has been developed to discuss the luminescence mechanisms in α-Al2O3:C,Mg in light of finding in this work.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116142 , vital:34323 , https://doi.org/10.1016/j.jlumin.2017.01.003
- Description: A comprehensive kinetic analysis of the glow peaks in α-Al2O3:C,Mg is reported. A thermoluminescence glow curve measured at 1 °C/s after beta irradiation to 1 Gy shows a high intensity peak hereafter referred to as the main peak at 161 °C and six lower intensity secondary peaks at 42, 72, 193, 279, 330, 370 °C respectively. For ease of reference, the secondary peaks are labelled as I, II, IV, V, VI and VII respectively and the main peak denoted peak III. Kinetic analysis of the glow peaks has been carried out using the initial rise, whole glow peak, peak shape, variable heating rate and glow curve deconvolution methods as well as by way of phosphorescence. Using Tm-Tstop, Tm-dose and phosphorescence analyses, the order of kinetics of the peaks has been evaluated as first order. Analysis by the peak shape, whole glow peak and deconvolution methods produce the same conclusion. The activation energy of peaks I through VII are calculated as ~0.83, 0.96, 1.37, 1.20, 1.15, 1.61 and 1.94 eV respectively. The frequency factors for all the peaks are of the order of 109 to 1014 s−1. The question of thermal quenching affecting the peaks was considered. The peaks III, IV and V, the only ones that could be conveniently studied in this regard, were found to be affected by thermal quenching. The activation energy for thermal quenching was calculated for peak III as 0.96±0.03 eV, for peak VI as 0.95±0.07 eV and for peak V as 1.26±0.08 eV. The thermal quenching phenomenon has been discussed with reference to F+ and F centres. An energy band model has been developed to discuss the luminescence mechanisms in α-Al2O3:C,Mg in light of finding in this work.
- Full Text: false
- Date Issued: 2017
Thermoluminescence of α-Al2O3: C, Mg annealed at 1200° C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018