Time-resolved luminescence: progress in development of theory and analytical methods
- Authors: Chithambo, Makaiko L
- Date: 2019
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/105403 , vital:32509 , https://doi.org/10.1142/9781786345790_0007
- Description: Time-resolved optical stimulation is an important method for measurement of optically stimulated luminescence. The aim of time-resolved optical stimulation is to separate the stimulation and emission of luminescence in time. The luminescence is stimulated from a sample using a short light pulse of constant intensity. The ensuing luminescence can be monitored either during stimulation in the presence of scattered stimulating light, or after the light-pulse. The time-resolved luminescence spectrum produced in this way can be resolved into components, each with a distinct lifetime. The lifetimes are linked to physical processes of luminescence. Time-resolved optical stimulation has thus been used to study dynamics of luminescence in various materials, particularly ones of interest in dosimetry such as quartz, feldspar, α-Al2O3:C and BeO. This chapter will review the theory of time-resolved luminescence, look at the instrumentation involved and discuss advances in analytical methods of time-resolved luminescence spectra.
- Full Text: false
- Date Issued: 2019
- Authors: Chithambo, Makaiko L
- Date: 2019
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/105403 , vital:32509 , https://doi.org/10.1142/9781786345790_0007
- Description: Time-resolved optical stimulation is an important method for measurement of optically stimulated luminescence. The aim of time-resolved optical stimulation is to separate the stimulation and emission of luminescence in time. The luminescence is stimulated from a sample using a short light pulse of constant intensity. The ensuing luminescence can be monitored either during stimulation in the presence of scattered stimulating light, or after the light-pulse. The time-resolved luminescence spectrum produced in this way can be resolved into components, each with a distinct lifetime. The lifetimes are linked to physical processes of luminescence. Time-resolved optical stimulation has thus been used to study dynamics of luminescence in various materials, particularly ones of interest in dosimetry such as quartz, feldspar, α-Al2O3:C and BeO. This chapter will review the theory of time-resolved luminescence, look at the instrumentation involved and discuss advances in analytical methods of time-resolved luminescence spectra.
- Full Text: false
- Date Issued: 2019
Time-resolved luminescence of low sensitivity quartz from crystalline rocks
- Chithambo, Makaiko L, Preusser, F, Ramseyer, K, Ogundare, F O
- Authors: Chithambo, Makaiko L , Preusser, F , Ramseyer, K , Ogundare, F O
- Date: 2007
- Language: English
- Type: text , article
- Identifier: vital:6801 , http://hdl.handle.net/10962/d1004164 , https://doi.org/10.1016/j.radmeas.2006.07.005
- Description: preprint , Time-resolved luminescence spectra of low sensitivity natural quartz from crystalline rocks are presented. The luminescence was pulse-stimulated at width using 470 nm blue light from quartz separated from plutonic, metamorphic, volcanic and hydrothermal samples. Measurements were made at 20 °C. All samples show evidence of a short lifetime component less than long although in several cases too weak in intensity to be evaluated accurately. On the other hand, the value of the principal lifetime component varies considerably being about in metamorphic quartz, in plutonic quartz, and in one example of hydrothermal quartz. The results illustrate a new feature of luminescence from quartz for which lifetimes less than or greater than have never been reported at room temperature before. It is argued that the thermal provenance of the quartz and so the annealing it will have experienced influences the size of the observed lifetime. In particular, the results are explained in terms of a model consisting of three luminescence centers with the dominant lifetime linked to preferential recombination at one center depending on the thermal history of the sample and hence the hole concentration of the center.
- Full Text:
- Date Issued: 2007
- Authors: Chithambo, Makaiko L , Preusser, F , Ramseyer, K , Ogundare, F O
- Date: 2007
- Language: English
- Type: text , article
- Identifier: vital:6801 , http://hdl.handle.net/10962/d1004164 , https://doi.org/10.1016/j.radmeas.2006.07.005
- Description: preprint , Time-resolved luminescence spectra of low sensitivity natural quartz from crystalline rocks are presented. The luminescence was pulse-stimulated at width using 470 nm blue light from quartz separated from plutonic, metamorphic, volcanic and hydrothermal samples. Measurements were made at 20 °C. All samples show evidence of a short lifetime component less than long although in several cases too weak in intensity to be evaluated accurately. On the other hand, the value of the principal lifetime component varies considerably being about in metamorphic quartz, in plutonic quartz, and in one example of hydrothermal quartz. The results illustrate a new feature of luminescence from quartz for which lifetimes less than or greater than have never been reported at room temperature before. It is argued that the thermal provenance of the quartz and so the annealing it will have experienced influences the size of the observed lifetime. In particular, the results are explained in terms of a model consisting of three luminescence centers with the dominant lifetime linked to preferential recombination at one center depending on the thermal history of the sample and hence the hole concentration of the center.
- Full Text:
- Date Issued: 2007
Time-resolved luminescence from quartz: an overview of contemporary developments and applications
- Chithambo, Makaiko L, Pagonis, Vasilis, Ankjærgaard, Christina
- Authors: Chithambo, Makaiko L , Pagonis, Vasilis , Ankjærgaard, Christina
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124743 , vital:35658 , https://doi.org/10.1016/j.physb.2015.10.014
- Description: Time-resolved optical stimulation of luminescence has become established as a key method for measurement of optically stimulated luminescence from quartz, feldspar and α-Al2O3:C, all materials of interest in dosimetry. The aim of time-resolved optical stimulation is to separate in time the stimulation and emission of luminescence. The luminescence is stimulated from a sample using a brief light pulse and the emission monitored during stimulation in the presence of scattered stimulating light or after pulsing, over photomultiplier noise only. Although the use of the method in retrospective dosimetry has been somewhat limited, the technique has been successfully applied to study mechanisms in the processes leading up to luminescence emission. The main means for this has been the temperature dependence of the luminescence intensity as well as the luminescence lifetimes determined from time-resolved luminescence spectra. In this paper we review some key developments in theory and applications to quartz including methods of evaluating lifetimes, techniques of evaluating kinetic parameters using both the dependence of luminescence intensity and lifetime on measurement temperature, and of lifetimes on annealing temperature. We then provide an overview of some notable applications such as separation of quartz signals from a quartz–feldspar admixture and the utility of the dynamic throughput, a measure of luminescence measured as a function of the pulse width. The paper concludes with some suggestions of areas where further exploration would advance understanding of dynamics of luminescence in quartz and help address some outstanding problems in its application.
- Full Text: false
- Date Issued: 2016
- Authors: Chithambo, Makaiko L , Pagonis, Vasilis , Ankjærgaard, Christina
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124743 , vital:35658 , https://doi.org/10.1016/j.physb.2015.10.014
- Description: Time-resolved optical stimulation of luminescence has become established as a key method for measurement of optically stimulated luminescence from quartz, feldspar and α-Al2O3:C, all materials of interest in dosimetry. The aim of time-resolved optical stimulation is to separate in time the stimulation and emission of luminescence. The luminescence is stimulated from a sample using a brief light pulse and the emission monitored during stimulation in the presence of scattered stimulating light or after pulsing, over photomultiplier noise only. Although the use of the method in retrospective dosimetry has been somewhat limited, the technique has been successfully applied to study mechanisms in the processes leading up to luminescence emission. The main means for this has been the temperature dependence of the luminescence intensity as well as the luminescence lifetimes determined from time-resolved luminescence spectra. In this paper we review some key developments in theory and applications to quartz including methods of evaluating lifetimes, techniques of evaluating kinetic parameters using both the dependence of luminescence intensity and lifetime on measurement temperature, and of lifetimes on annealing temperature. We then provide an overview of some notable applications such as separation of quartz signals from a quartz–feldspar admixture and the utility of the dynamic throughput, a measure of luminescence measured as a function of the pulse width. The paper concludes with some suggestions of areas where further exploration would advance understanding of dynamics of luminescence in quartz and help address some outstanding problems in its application.
- Full Text: false
- Date Issued: 2016
Thermoluminescence properties of potassium fluoride:
- Ogundare, F O, Folley, Damilola E, Chithambo, Makaiko L, Arise, T O
- Authors: Ogundare, F O , Folley, Damilola E , Chithambo, Makaiko L , Arise, T O
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160500 , vital:40451 , https://doi.org/10.1016/j.nimb.2020.09.009
- Description: This study is designed to examine the thermoluminescence characteristics of potassium fluoride for possible use as a thermoluminescence dosemeter. Thermoluminescence measurements were carried out at doses up to 20 Gy and heating rates between 0.2 and 4°C/s. The glow curve of the fluoride, readout at 1°Cs−1, exhibited two peaks at 130 and 250 °C. In addition, two shoulder peaks appeared at 70 and 200°C.
- Full Text:
- Date Issued: 2020
- Authors: Ogundare, F O , Folley, Damilola E , Chithambo, Makaiko L , Arise, T O
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160500 , vital:40451 , https://doi.org/10.1016/j.nimb.2020.09.009
- Description: This study is designed to examine the thermoluminescence characteristics of potassium fluoride for possible use as a thermoluminescence dosemeter. Thermoluminescence measurements were carried out at doses up to 20 Gy and heating rates between 0.2 and 4°C/s. The glow curve of the fluoride, readout at 1°Cs−1, exhibited two peaks at 130 and 250 °C. In addition, two shoulder peaks appeared at 70 and 200°C.
- Full Text:
- Date Issued: 2020
Thermoluminescence of α-Al2O3: C, Mg: kinetic analysis of the main glow peak
- 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/10962/119844 , vital:34788 , https://doi.org/10.1016/j.jlumin.2016.10.031
- Description: The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1 °C/s following beta irradiation to 1 Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161 °C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370 °C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main 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 ~1.36 eV and the frequency factor of the order of 1014 s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08 eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.
- 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/10962/119844 , vital:34788 , https://doi.org/10.1016/j.jlumin.2016.10.031
- Description: The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1 °C/s following beta irradiation to 1 Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161 °C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370 °C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main 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 ~1.36 eV and the frequency factor of the order of 1014 s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08 eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.
- 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
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 the main peak in SrAl2O4: Eu2+, Dy3+: spectral and kinetics features of secondary emission detected in the ultra-violet region
- Authors: Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124197 , vital:35575 , https://doi.org/10.1016/j.radmeas.2016.12.001
- Description: We report the thermoluminescence of SrAl2O4:Eu2+,Dy3+ measured in the ultra-violet region of the spectrum between 300 and 400 nm. Complementary measurements of X-ray excited optical luminescence confirm emission bands of stimulated luminescence in this region. As a further test, optically stimulated luminescence was also measured in this region. The glow curve measured at 1 °C s−1 following irradiation to various doses appears simple and single but is in reality a collection of several components. This was shown by results from the Tm-Tstop method on both ends of the peak, application of thermal cleaning beyond the peak maximum as well as the dependence of the peak on fading. The latter shows that new peaks appear as preceding ones fade. Kinetic analysis of some of the main peaks was carried out giving an activation energy of 0.6 eV. The implication of the results on measurement of phosphorescence, interpretation of dose response and fading is discussed.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124197 , vital:35575 , https://doi.org/10.1016/j.radmeas.2016.12.001
- Description: We report the thermoluminescence of SrAl2O4:Eu2+,Dy3+ measured in the ultra-violet region of the spectrum between 300 and 400 nm. Complementary measurements of X-ray excited optical luminescence confirm emission bands of stimulated luminescence in this region. As a further test, optically stimulated luminescence was also measured in this region. The glow curve measured at 1 °C s−1 following irradiation to various doses appears simple and single but is in reality a collection of several components. This was shown by results from the Tm-Tstop method on both ends of the peak, application of thermal cleaning beyond the peak maximum as well as the dependence of the peak on fading. The latter shows that new peaks appear as preceding ones fade. Kinetic analysis of some of the main peaks was carried out giving an activation energy of 0.6 eV. The implication of the results on measurement of phosphorescence, interpretation of dose response and fading is discussed.
- Full Text: false
- Date Issued: 2017
Thermoluminescence of SrAl2O4: Eu2+, Dy3+: kinetic analysis of a composite-peak
- Chithambo, Makaiko L, Wako, A H, Finch, A A
- Authors: Chithambo, Makaiko L , Wako, A H , Finch, A A
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124157 , vital:35571 , https://doi.org/10.1016/j.radmeas.2016.12.009
- Description: The kinetic analysis of thermoluminescence of beta-irradiated SrAl2O4:Eu2+,Dy3+ is reported. The glow-curve is dominated by an apparently-single peak. It has been demonstrated using a number of tests including partial dynamic-heating, isothermal heating, phosphorescence and, the effect of fading, that the peak and the glow-curve consists of a set of closely-spaced peaks. In view of the peak being complex, its first few components were abstracted and analysed and for comparison, the peak was also analysed assuming it is genuinely single.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L , Wako, A H , Finch, A A
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124157 , vital:35571 , https://doi.org/10.1016/j.radmeas.2016.12.009
- Description: The kinetic analysis of thermoluminescence of beta-irradiated SrAl2O4:Eu2+,Dy3+ is reported. The glow-curve is dominated by an apparently-single peak. It has been demonstrated using a number of tests including partial dynamic-heating, isothermal heating, phosphorescence and, the effect of fading, that the peak and the glow-curve consists of a set of closely-spaced peaks. In view of the peak being complex, its first few components were abstracted and analysed and for comparison, the peak was also analysed assuming it is genuinely single.
- Full Text: false
- Date Issued: 2017
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
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
Thermoluminescence of annealed synthetic quartz: the influence of annealing on kinetic parameters and thermal quenching
- Dawam, Robert R, Chithambo, Makaiko L
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
Thermally-assisted optically stimulated luminescence from deep electron traps in α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L, Polymeris, G S
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L , Polymeris, G S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116133 , vital:34322 , https://doi.org/10.1016/j.nimb.2017.04.075
- Description: We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al2O3:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al2O3:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L , Polymeris, G S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116133 , vital:34322 , https://doi.org/10.1016/j.nimb.2017.04.075
- Description: We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al2O3:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al2O3:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.
- Full Text: false
- Date Issued: 2017
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
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
The influence of dose on the kinetic parameters and dosimetric features of the main thermoluminescence glow 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/10962/119834 , vital:34787 , https://doi.org/10.1016/j.nimb.2016.12.027
- Description: The influence of dose (0.1–100 Gy) on the kinetic parameters and the dosimetric features of the main glow peak of α-Al2O3:C,Mg have been investigated. Thermoluminescence (TL) measured at 1 °C/s shows a very high intensity glow peak at 161 °C and six secondary peaks at 42, 72, 193, 279, 330, 370 °C respectively. Analysis shows that the main peak follows first order kinetics irrespective of the irradiation dose. The activation energy is found to be consistent at 1.37 eV and the frequency factor is of the order of 1014 s−1 for any dose between 0.1 and 100 Gy. Further, the analysis for thermal quenching of the main peak of 0.1 Gy irradiated sample shows that the activation energy for thermal quenching is (0.94 ± 0.04) eV.
- 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/10962/119834 , vital:34787 , https://doi.org/10.1016/j.nimb.2016.12.027
- Description: The influence of dose (0.1–100 Gy) on the kinetic parameters and the dosimetric features of the main glow peak of α-Al2O3:C,Mg have been investigated. Thermoluminescence (TL) measured at 1 °C/s shows a very high intensity glow peak at 161 °C and six secondary peaks at 42, 72, 193, 279, 330, 370 °C respectively. Analysis shows that the main peak follows first order kinetics irrespective of the irradiation dose. The activation energy is found to be consistent at 1.37 eV and the frequency factor is of the order of 1014 s−1 for any dose between 0.1 and 100 Gy. Further, the analysis for thermal quenching of the main peak of 0.1 Gy irradiated sample shows that the activation energy for thermal quenching is (0.94 ± 0.04) eV.
- 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
The effect of pre-dose on thermally and optically stimulated luminescence from α-Al2O3C, Mg and α-Al2O3: 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/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
- Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
- 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/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
- Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
- 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
Temperature-dependence of time-resolved optically stimulated luminescence and composition heterogeneity of synthetic α-Al2O3: C
- Chithambo, Makaiko L, Costin, G
- Authors: Chithambo, Makaiko L , Costin, G
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124172 , vital:35573 , https://doi.org/10.1016/j.jlumin.2016.10.038
- Description: The relationship of pulse-width, lifetime and measurement temperature in describing intensity of time-resolved luminescence optically stimulated at 470 nm from α-Al2O3:C is reported. The change of luminescence intensity with stimulation temperature is discussed in terms of the signal integrated over a complete time-resolved luminescence spectrum or in terms of ratios of the signal emitted either during or after pulsed stimulation to the total signal obtained per spectrum. The temperature-induced change in these parameters depends on whether the pulse-width is less or more than the luminescence lifetime. This is because the lifetime in α-Al2O3:C varies with measurement temperature. We have developed and applied new models to distinguish thermal assistance from different traps and to use this information as an additional means to analyse thermal quenching by using the luminescence intensity integrated from time-resolved spectra. Using a model based on use of the throughput, the activation energy for thermal assistance was determined for the shallow trap as 0.054±0.001 eV and as 0.53±0.03 eV for the main trap. The activation energy for thermal quenching was then evaluated using luminescence yield during the pulse as 1.09±0.01 eV and as 1.12±0.01 eV using the throughput after the pulse. Using the new analytical method based on integrated intensity, the activation energy for thermal quenching was found as 1.00±0.07 eV. These values are self-consistent and show that the methods for analyzing temperature-induced changes in intensity and the attendant thermal effects, such as thermal assistance can be successfully applied. We have also reported a general mathematical model that accounts for the temperature-dependence of time-resolved luminescence from α-Al2O3:C. The luminescence study was complemented by investigation of the phase and composition heterogeneity of the samples.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L , Costin, G
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124172 , vital:35573 , https://doi.org/10.1016/j.jlumin.2016.10.038
- Description: The relationship of pulse-width, lifetime and measurement temperature in describing intensity of time-resolved luminescence optically stimulated at 470 nm from α-Al2O3:C is reported. The change of luminescence intensity with stimulation temperature is discussed in terms of the signal integrated over a complete time-resolved luminescence spectrum or in terms of ratios of the signal emitted either during or after pulsed stimulation to the total signal obtained per spectrum. The temperature-induced change in these parameters depends on whether the pulse-width is less or more than the luminescence lifetime. This is because the lifetime in α-Al2O3:C varies with measurement temperature. We have developed and applied new models to distinguish thermal assistance from different traps and to use this information as an additional means to analyse thermal quenching by using the luminescence intensity integrated from time-resolved spectra. Using a model based on use of the throughput, the activation energy for thermal assistance was determined for the shallow trap as 0.054±0.001 eV and as 0.53±0.03 eV for the main trap. The activation energy for thermal quenching was then evaluated using luminescence yield during the pulse as 1.09±0.01 eV and as 1.12±0.01 eV using the throughput after the pulse. Using the new analytical method based on integrated intensity, the activation energy for thermal quenching was found as 1.00±0.07 eV. These values are self-consistent and show that the methods for analyzing temperature-induced changes in intensity and the attendant thermal effects, such as thermal assistance can be successfully applied. We have also reported a general mathematical model that accounts for the temperature-dependence of time-resolved luminescence from α-Al2O3:C. The luminescence study was complemented by investigation of the phase and composition heterogeneity of the samples.
- Full Text: false
- Date Issued: 2017