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
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
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
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
Features of an annealing-induced thermoluminescence peak in 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/10962/116013 , vital:34289 , DOI: 10.1016/j.optmat.2017.05.034
- Description: We report the thermoluminescence glow curves of beta irradiated single crystal α-Al2O3:C,Mg after annealing at 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy following annealing at 700 and 900 °C shows a high intensity peak at 163 °C and seven secondary peaks of weaker intensity at 43, 73, 100, 195, 280, 329 and 370 °C. Comparing the position of the peaks in the annealed samples with those in an un-annealed one, it is observed that the peak at 100 °C appears only after annealing at and above 700 °C. Kinetic analysis of this annealing-induced peak was carried out using the initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the peak was determined as first order using various methods including the Tm-Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about 1.01 eV and the frequency factor of the order of 1012 s−1. The peak was found to be affected by thermal quenching in analysis based on change of peak intensity with heating rate. The activation energy of thermal quenching was evaluated as 1.06 ± 0.08 eV. We speculate that the annealing-induced peak is due to formation of a new electron trap after destruction of the F22+(2 Mg) centre when the sample is annealed at 700 °C. The annealing-induced peak fades with storage between irradiation and measurement. It was also concluded that electrons from traps corresponding to secondary peaks get re-trapped at the main electron trap.
- 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/10962/116013 , vital:34289 , DOI: 10.1016/j.optmat.2017.05.034
- Description: We report the thermoluminescence glow curves of beta irradiated single crystal α-Al2O3:C,Mg after annealing at 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy following annealing at 700 and 900 °C shows a high intensity peak at 163 °C and seven secondary peaks of weaker intensity at 43, 73, 100, 195, 280, 329 and 370 °C. Comparing the position of the peaks in the annealed samples with those in an un-annealed one, it is observed that the peak at 100 °C appears only after annealing at and above 700 °C. Kinetic analysis of this annealing-induced peak was carried out using the initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the peak was determined as first order using various methods including the Tm-Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about 1.01 eV and the frequency factor of the order of 1012 s−1. The peak was found to be affected by thermal quenching in analysis based on change of peak intensity with heating rate. The activation energy of thermal quenching was evaluated as 1.06 ± 0.08 eV. We speculate that the annealing-induced peak is due to formation of a new electron trap after destruction of the F22+(2 Mg) centre when the sample is annealed at 700 °C. The annealing-induced peak fades with storage between irradiation and measurement. It was also concluded that electrons from traps corresponding to secondary peaks get re-trapped at the main electron trap.
- Full Text: false
- Date Issued: 2017
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
Influence of annealing on thermoluminescence of natural quartz: kinetic analysis and experimental study of apparent inverse thermal quenching
- Folley, Damilola E, Chithambo, Makaiko L
- Authors: Folley, Damilola E , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109996 , vital:33212 , https://doi.org/10.1016/j.radmeas.2018.04.010
- Description: The influence of annealing on the main thermoluminescence glow-peak of natural quartz is reported. For comparison, results from un-annealed quartz are included. The glow-curve measured at 1 °Cs−1 after beta irradiation to 50 Gy revealed six peaks each for quartz annealed at 800 °C for 1 h and the un-annealed sample. The main peak in both quartzes was observed at 72 °C. This report focusses on kinetic analysis of the main peak. The analysis was carried out using various methods consisting of the initial rise, whole glow-peak, peak shape, variable heating rate and phosphorescence-based methods. The activation energy obtained using the various methods ranges between and for the annealed sample and between and for the un-annealed sample. The result suggests that annealing has little effect on the activation energy. The luminescence intensity decreased with heating rate in the un-annealed sample in a manner suggestive of thermal quenching. In contrast, the dependence of intensity on heating rate in the annealed sample is influenced by the dose the sample is irradiated to. Whereas thermal quenching was noted for a dose of 50 Gy in the un-annealed sample, the annealed sample showed evidence of thermal quenching at a low dose of 3 Gy with the opposite effect when irradiated to 50 Gy. The activation energies of thermal quenching were found as and for the un-annealed and annealed samples respectively. We ascribe the apparent dependence of thermal quenching on dose in the annealed sample to competition between radiative and non-radiative transitions at the recombination centre.
- Full Text: false
- Date Issued: 2018
- Authors: Folley, Damilola E , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109996 , vital:33212 , https://doi.org/10.1016/j.radmeas.2018.04.010
- Description: The influence of annealing on the main thermoluminescence glow-peak of natural quartz is reported. For comparison, results from un-annealed quartz are included. The glow-curve measured at 1 °Cs−1 after beta irradiation to 50 Gy revealed six peaks each for quartz annealed at 800 °C for 1 h and the un-annealed sample. The main peak in both quartzes was observed at 72 °C. This report focusses on kinetic analysis of the main peak. The analysis was carried out using various methods consisting of the initial rise, whole glow-peak, peak shape, variable heating rate and phosphorescence-based methods. The activation energy obtained using the various methods ranges between and for the annealed sample and between and for the un-annealed sample. The result suggests that annealing has little effect on the activation energy. The luminescence intensity decreased with heating rate in the un-annealed sample in a manner suggestive of thermal quenching. In contrast, the dependence of intensity on heating rate in the annealed sample is influenced by the dose the sample is irradiated to. Whereas thermal quenching was noted for a dose of 50 Gy in the un-annealed sample, the annealed sample showed evidence of thermal quenching at a low dose of 3 Gy with the opposite effect when irradiated to 50 Gy. The activation energies of thermal quenching were found as and for the un-annealed and annealed samples respectively. We ascribe the apparent dependence of thermal quenching on dose in the annealed sample to competition between radiative and non-radiative transitions at the recombination centre.
- Full Text: false
- Date Issued: 2018
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
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
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
On the sensitivity of thermally and optically stimulated luminescence of α-Al2O3: C and 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/10962/119803 , vital:34784 , https://doi.org/10.1016/j.radmeas.2017.03.006
- Description: The luminescence sensitivity of α-Al2O3:C and α-Al2O3:C, Mg is of interest because of the contemporary use of these materials in dosimetry related applications. We report investigations concerning the change in sensitivity of thermoluminescence (TL) and optically stimulated luminescence (OSL) from α-Al2O3:C and α-Al2O3:C, Mg with re-use. The study was carried out on a set of un-annealed samples and others annealed at 700 and 900 °C. The TL and OSL sensitivity in α-Al2O3:C and α-Al2O3:C, Mg was found to increase with sample re-use whether the intensity was monitored as peak area or peak height for the main TL peak or, in the case of OSL, as the maximum intensity or the area under a decay curve. The fractional increase in area under either the main TL peak or the OSL decay curve exceeds that of the TL peak height or maximum OSL intensity when samples are re-used. However, when un-annealed samples are used, any increase in TL peak height or peak area per measurement is less than observed in annealed samples. It is also interesting to note that the change in maximum OSL intensity or OSL area is minimal for samples annealed at 900 °C. In general, the TL sensitivity in α-Al2O3:C increases more than that in α-Al2O3:C, Mg with re-use. On the other hand, the OSL sensitivity in α-Al2O3:C, Mg increases more than that in α-Al2O3:C with re-use. These findings suggest that it is advisable to take into account the fractional increase in sensitivity per measurement when one uses α-Al2O3:C as a TL dosimeter and α-Al2O3:C, Mg as an OSL dosimeter.
- 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/10962/119803 , vital:34784 , https://doi.org/10.1016/j.radmeas.2017.03.006
- Description: The luminescence sensitivity of α-Al2O3:C and α-Al2O3:C, Mg is of interest because of the contemporary use of these materials in dosimetry related applications. We report investigations concerning the change in sensitivity of thermoluminescence (TL) and optically stimulated luminescence (OSL) from α-Al2O3:C and α-Al2O3:C, Mg with re-use. The study was carried out on a set of un-annealed samples and others annealed at 700 and 900 °C. The TL and OSL sensitivity in α-Al2O3:C and α-Al2O3:C, Mg was found to increase with sample re-use whether the intensity was monitored as peak area or peak height for the main TL peak or, in the case of OSL, as the maximum intensity or the area under a decay curve. The fractional increase in area under either the main TL peak or the OSL decay curve exceeds that of the TL peak height or maximum OSL intensity when samples are re-used. However, when un-annealed samples are used, any increase in TL peak height or peak area per measurement is less than observed in annealed samples. It is also interesting to note that the change in maximum OSL intensity or OSL area is minimal for samples annealed at 900 °C. In general, the TL sensitivity in α-Al2O3:C increases more than that in α-Al2O3:C, Mg with re-use. On the other hand, the OSL sensitivity in α-Al2O3:C, Mg increases more than that in α-Al2O3:C with re-use. These findings suggest that it is advisable to take into account the fractional increase in sensitivity per measurement when one uses α-Al2O3:C as a TL dosimeter and α-Al2O3:C, Mg as an OSL dosimeter.
- Full Text: false
- Date Issued: 2017
Optically stimulated luminescence of ultra-high molecular weight polyethylene: a study of dosimetric features
- Chithambo, Makaiko L, Kalita, Jitumani M
- Authors: Chithambo, Makaiko L , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110035 , vital:33217 , https://doi.org/10.1016/j.radmeas.2018.06.006
- Description: We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.
- Full Text: false
- Date Issued: 2018
- Authors: Chithambo, Makaiko L , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110035 , vital:33217 , https://doi.org/10.1016/j.radmeas.2018.06.006
- Description: We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.
- Full Text: false
- Date Issued: 2018
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
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
Phototransferred thermoluminescence in α-Al2O3: C, Mg under 470 nm blue light stimulation
- 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/10962/116026 , vital:34290 , https://doi.org/10.1016/j.jlumin.2017.04.059
- Description: Phototransferred thermoluminescence (PTTL) in α-Al2O3:C,Mg under 470 nm blue light has been investigated. Conventional thermoluminescence (TL) measured at 1 °C/s following irradiation to 10 Gy shows the main peak (labelled as III) at 163 °C and six secondary peaks I, II, IV, V, VI and VII at 45, 74, 200, 279, 328, 370 °C respectively. When a sample irradiated to 10 Gy is preheated to 220 °C at 1 °C/s to remove peaks I, II, III and IV and then exposed to 470 nm blue light for 100 s, it is found that three peaks I, II and III are reproduced under phototransfer. Kinetic analysis of the PTTL peaks shows that their kinetic parameters are similar to those of peaks I, II and III from conventional TL. Pulse annealing experiments, intended to study the dependence of PTTL peak intensity on preheating temperature, show that the electron traps corresponding to peaks V, VI and VII act as donor traps whereas the traps corresponding to peaks I, II and III act as acceptor traps. Further, it was found that no PTTL can be generated when all the traps corresponding to peaks I, II…VII are erased by preheating after irradiation. The primary conclusion here is that α-Al2O3:C,Mg does not have any deep traps beyond 400 °C sensitive to 470 nm stimulation or if there are any, their concentration is negligible. The PTTL for any of the PTTL peaks mentioned earlier increases with illumination time to a maximum within 400 s for measurements corresponding to doses between 6 and 15 Gy. The dose response of PTTL peaks II and III is linear within 1–15 Gy. Regarding fading, PTTL peak II fades to background level within 18000 s whereas in the same time, PTTL peak III fades down to 40% of its initial intensity.
- 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/10962/116026 , vital:34290 , https://doi.org/10.1016/j.jlumin.2017.04.059
- Description: Phototransferred thermoluminescence (PTTL) in α-Al2O3:C,Mg under 470 nm blue light has been investigated. Conventional thermoluminescence (TL) measured at 1 °C/s following irradiation to 10 Gy shows the main peak (labelled as III) at 163 °C and six secondary peaks I, II, IV, V, VI and VII at 45, 74, 200, 279, 328, 370 °C respectively. When a sample irradiated to 10 Gy is preheated to 220 °C at 1 °C/s to remove peaks I, II, III and IV and then exposed to 470 nm blue light for 100 s, it is found that three peaks I, II and III are reproduced under phototransfer. Kinetic analysis of the PTTL peaks shows that their kinetic parameters are similar to those of peaks I, II and III from conventional TL. Pulse annealing experiments, intended to study the dependence of PTTL peak intensity on preheating temperature, show that the electron traps corresponding to peaks V, VI and VII act as donor traps whereas the traps corresponding to peaks I, II and III act as acceptor traps. Further, it was found that no PTTL can be generated when all the traps corresponding to peaks I, II…VII are erased by preheating after irradiation. The primary conclusion here is that α-Al2O3:C,Mg does not have any deep traps beyond 400 °C sensitive to 470 nm stimulation or if there are any, their concentration is negligible. The PTTL for any of the PTTL peaks mentioned earlier increases with illumination time to a maximum within 400 s for measurements corresponding to doses between 6 and 15 Gy. The dose response of PTTL peaks II and III is linear within 1–15 Gy. Regarding fading, PTTL peak II fades to background level within 18000 s whereas in the same time, PTTL peak III fades down to 40% of its initial intensity.
- Full Text: false
- Date Issued: 2017
Phototransferred thermoluminescence of synthetic quartz: analysis of illumination-time response curves
- Chithambo, Makaiko L, Niyonzima, P, Kalita, Jitumani M
- Authors: Chithambo, Makaiko L , Niyonzima, P , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111020 , vital:33364 , https://doi.org/10.1016/j.jlumin.2018.02.029
- Description: Phototransferred thermoluminescence (PTTL) induced in synthetic quartz by 470 nm blue light is reported. The glow curve measured at 5 °C/s up to 500 °C after irradiation to 100 Gy shows six peaks at 94, 116, 175, 212, 280 and 348 °C labelled I through VI and another one at 80 °C (labelled A1). PTTL is only observed for peaks A1 and I and is induced at peak A1 as long as peak III has been removed by preheating and at peak I after preheating to deplete peak VI. The inducement of PTTL even when all peaks have been removed points to deep electron traps in the quartz also acting as donors in addition to the putative ones below 500 °C. The PTTL intensity as a function of duration of illumination for A1 goes through a peak and decreases monotonically or to a stable value depending on the preheating temperature. The change of PTTL intensity as a function of illumination time is described using a set of coupled linear differential equations. The number of acceptors and donors in a particular system described in this way is influenced by the preheating temperature.
- Full Text: false
- Date Issued: 2018
- Authors: Chithambo, Makaiko L , Niyonzima, P , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111020 , vital:33364 , https://doi.org/10.1016/j.jlumin.2018.02.029
- Description: Phototransferred thermoluminescence (PTTL) induced in synthetic quartz by 470 nm blue light is reported. The glow curve measured at 5 °C/s up to 500 °C after irradiation to 100 Gy shows six peaks at 94, 116, 175, 212, 280 and 348 °C labelled I through VI and another one at 80 °C (labelled A1). PTTL is only observed for peaks A1 and I and is induced at peak A1 as long as peak III has been removed by preheating and at peak I after preheating to deplete peak VI. The inducement of PTTL even when all peaks have been removed points to deep electron traps in the quartz also acting as donors in addition to the putative ones below 500 °C. The PTTL intensity as a function of duration of illumination for A1 goes through a peak and decreases monotonically or to a stable value depending on the preheating temperature. The change of PTTL intensity as a function of illumination time is described using a set of coupled linear differential equations. The number of acceptors and donors in a particular system described in this way is influenced by the preheating temperature.
- Full Text: false
- Date Issued: 2018
Phototransferred thermoluminescence of α-Al2O3: C: experimental results and empirical models
- Chithambo, Makaiko L, Seneza, Cleophace, Kalita, Jitumani M
- Authors: Chithambo, Makaiko L , Seneza, Cleophace , Kalita, Jitumani M
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115681 , vital:34215 , https://doi.org/10.1016/j.radmeas.2017.08.009
- Description: The thermoluminescence glow curve of α-Al2O3:C consists of a prominent apparently-single peak and a number of weaker intensity secondary peaks. Phototransferred thermoluminescence (PTTL) from secondary glow peaks in α-Al2O3:C is reported. For completeness and to aid discussion, complementary results for the main peak are included. The problem studied is one of phototransferred thermoluminescence for a system of multiple acceptors and multiple donors. A TL glow curve recorded at 5 °C/s following irradiation to 0.5 Gy shows the main peak (labelled II) at 240 °C and two secondary peaks at 86 °C (peak I) and 360 °C (peak III). Peak I is reproduced under phototransfer after any preheating between 100 and 500 °C. Peak II is also reproduced as a PTTL peak after preheating to any temperature up to 800 °C. For the latter, the duration of preheating matters because if the sample is preheated at 800 °C for say, 6 min, PTTL is obtained but not when this is extended to say, 15 min. No PTTL was observed from peak III at all. A study of the time dependence of the PTTL intensity from peak III, following preheating that removes peaks I and II, shows that its electron trap acts as an acceptor when the duration of illumination to stimulate electrons from deep traps is brief but that when the illumination time is extended, the electron trap for peak III loses some of its trapped electrons to the shallower traps thus acting as a donor trap.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L , Seneza, Cleophace , Kalita, Jitumani M
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115681 , vital:34215 , https://doi.org/10.1016/j.radmeas.2017.08.009
- Description: The thermoluminescence glow curve of α-Al2O3:C consists of a prominent apparently-single peak and a number of weaker intensity secondary peaks. Phototransferred thermoluminescence (PTTL) from secondary glow peaks in α-Al2O3:C is reported. For completeness and to aid discussion, complementary results for the main peak are included. The problem studied is one of phototransferred thermoluminescence for a system of multiple acceptors and multiple donors. A TL glow curve recorded at 5 °C/s following irradiation to 0.5 Gy shows the main peak (labelled II) at 240 °C and two secondary peaks at 86 °C (peak I) and 360 °C (peak III). Peak I is reproduced under phototransfer after any preheating between 100 and 500 °C. Peak II is also reproduced as a PTTL peak after preheating to any temperature up to 800 °C. For the latter, the duration of preheating matters because if the sample is preheated at 800 °C for say, 6 min, PTTL is obtained but not when this is extended to say, 15 min. No PTTL was observed from peak III at all. A study of the time dependence of the PTTL intensity from peak III, following preheating that removes peaks I and II, shows that its electron trap acts as an acceptor when the duration of illumination to stimulate electrons from deep traps is brief but that when the illumination time is extended, the electron trap for peak III loses some of its trapped electrons to the shallower traps thus acting as a donor trap.
- Full Text: false
- Date Issued: 2017
Radioluminescence of annealed synthetic quartz
- Chithambo, Makaiko L, Niyonzima, P
- Authors: Chithambo, Makaiko L , Niyonzima, P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115504 , vital:34150 , https://doi.org/10.1016/j.radmeas.2017.02.005
- Description: The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L , Niyonzima, P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115504 , vital:34150 , https://doi.org/10.1016/j.radmeas.2017.02.005
- Description: The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.
- 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
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