Method of Hoogenstraaten as a tool for obtaining the trap parameters of general-order thermoluminescence glow peaks

The Hoogenstraaten method is a technique that uses various heating rates for obtaining the activation energy E (eV) in the case of first-order thermoluminescence glow peaks. This method can also be used for obtaining E (eV) for all types of glow peaks regardless of their kinetics order (b). The present work shows that the intercept of the Hoogenstraaten relation, which is usually used for obtaining the frequency factor S (s ^?1) of the first-order glow peak, can be used as a very good approximation to obtain the pre-exponential factor S ^{′ ′} (s ^?1) in the case of general-order glow peaks, when one uses Hoogenstraaten’s method to obtain E (eV). In addition, the present work suggests a numerical method for obtaining the kinetics order of the general-order glow peak. The method depends on the activation energy E (eV) obtained by the Hoogenstraaten method and the above-mentioned approximation for obtaining the pre-exponential factor S ^{′ ′} (s ^?1). An independent evaluation of the suggested methods for obtaining the trap parameters, the activation energy E (eV), the pre-exponential factor S ^{′ ′} (s ^?1) and the kinetics order (b) is illustrated here by taking a numerically computed glow peak and applying a one-trap and one-recombination-center model.     

Applications of the three points analysis method for obtaining the trap parameters and the separation of thermoluminescence glow curve into its components

Here, we apply a recently developed technique to separate a composite thermoluminescence (TL) glow curve into its individual components and to evaluate the trap parameters of the individual TL glow peaks. These parameters include the order of kinetics b, the activation energy E (eV) and the frequency factor S (s^?1) or the pre-exponential factor S″ (s^?1). Recently, a general equation was developed to estimate the order of kinetics b. The characteristic point of this equation is that any set of three data points in a TL glow curve can yield b. Using this characteristic, an improved procedure was suggested to separate a composite glow curve, which includes several overlapping peaks, into its individual components and to obtain the trap parameters of the individual glow peaks. The method was applied here to analyze and determine the trap parameters of the TL glow curve of the promising TL dosimetric material, double potassium yttrium fluoride (K₂YF₅) doped with praseodymium ions (Pr³⁺), in response to γ-irradiation.     

Two-point method for kinetic analysis of a thermoluminescence glow peak

We present a method for the estimation of defect (trap) physical parameters from thermoluminescence (TL) glow peaks. In this method, the order of kinetics b is determined using two values of TL intensity each of which corresponds to the same temperature (T ₁) on two separate glow peaks of a phosphor. The two glow peaks are obtained from two aliquots of the phosphor irradiated to same dose but read out at different heating rates. The proposed method requires a minimum of only two data points in contrast to standard peak shape (PS) methods that require three points corresponding to three different temperatures on the same glow peak. Once the order of kinetics b is determined, the activation energy E is calculated by taking a second point (T ₂) on any one of the two glow peaks. The values of b and E thus obtained are used to evaluate the frequency factor S ^′′ and the number of trapped electrons before the heating begins n _o. The validity of the method was checked using two numerically generated glow peaks. For the two cases, the method reproduced the input values reasonably well. The method was also used to analyse two experimental glow peaks. The results obtained provide a reasonably good fit to the experimental data. The kinetic parameters calculated using the present technique are comparable to those calculated using PS and initial rise methods. Initial guesses can easily be obtained for E and S ^′′ using the present technique when a glow curve is to be deconvoluted with a model consisting of many unknown parameters with E and S″ inclusive.     

Thermoluminescence kinetic study of binary lead-silicate glasses

This paper describes a detailed experimental study of the thermoluminescence (TL) properties of four binary lead-silicate glasses, with PbO concentrations ranging from 32% to 62% in mole percent. The TL glow peaks between room temperature and 300 °C were analyzed using a systematic thermal cleaning technique. The T_max-T_stop and E-T_stop methods of analysis were used to identify the number of peaks under the glow curves, and to obtain the activation energy E for each TL trap. A computerized glow curve fitting analysis is used to fit the experimental data to four first-order peaks with maxima at temperatures of 54, 80, 110 and 210 °C, as measured with a heating rate of 2 °C/s. The kinetic parameters of the glow-peak at 210 °C were confirmed by using phosphorescence decay methods of analysis. The TL traps associated with the low-temperature TL peak at 54 °C are found to depend strongly on the PbO concentration of the samples, while the higher-temperature TL peaks show a behavior independent of the PbO concentration. The activation energy E and frequency factor s of the low-temperature TL trap associated with the peak at 54 °C are consistent with a trap involving a delocalized transition through the conduction band. However, the activation energies and frequency factors for the higher-temperature TL traps are consistent with traps involving localized transitions via an excited state below the conduction band. The data suggest that these higher-temperature TL traps are associated with the common silicate matrix in these binary silicate glasses.     

Determination of thermoluminescence kinetic parameters of thulium doped lithium calcium borate

For the first time kinetic parameters of thulium doped Lithium calcium borate (LCB) Thermoluminescence (TL) material are reported here. Irradiated LCB:Tm³⁺ powder has revealed two intense TL glow peaks one at 510 (peak 1) and the other at 660 K (peak 2). Activation energy (E), frequency factor (s) and order of kinetics (b) of these peaks were determined by various heating rate (VHR), initial rise (IR), and peak shape (PS) methods. The trap depth and frequency factor determined for peaks 1 and 2 of LCB:Tm phosphor using VHR and IR methods are in good agreement. The average activation energy of peaks 1 and 2 obtained by these methods is 1.62 and 1.91 eV respectively. The frequency factors of peaks 1 and 2 are in the range of 10^13–16 and 10^12–14 sec⁻¹ respectively. The E and s values estimated using the glow peak shape dependent parameters are relatively less compared to the values obtained from other methods. The large difference in these values is due to the complex nature of the glow curves. The order of the kinetics process for complex glow curve peaks could not be assigned on the basis of shape parameters alone but T_m response on absorbed dose is to be considered for final confirmation. Glow peaks 1 and 2 of LCB:Tm³⁺ obey first and general order kinetics respectively.     

The analysis of thermoluminescent glow peaks of copper doped ZnS thin films after β-irradiation

In the given study, the thermoluminescence (TL) properties of copper (Cu)-doped ZnS thin films were investigated after β-irradiation at room temperature (RT). It was observed that the glow curve of this material has two broad TL peaks, in which one of them was centered at about 110 °C and the other at about 170 °C for a heating rate of 1 °C s⁻¹ in the temperature range from RT to 350 °C. The additive dose (AD), T_m(E_a)−T_stop, repeated initial rise (RIR), variable heating rate (VHR) and computerized glow curve deconvolution (CGCD) methods were used to analyze its glow curves. These methods indicated that the glow curve of this material is the superposition of a number of first- and general-order glow peaks, or at least due to the distribution of traps. The dose responses and fading process of both peaks were also examined, and it was observed that the dose responses of both peaks have similar pattern. First they follow a good linearity with different slopes and then saturate at approximately same dose level (2 kGy). The low-temperature broad peak nearly disappeared after 1 week storage in the dark at RT. On the other hand, the intensity of the high-temperature broad peak was approximately reduced to 50% of its original value. The TL emission spectrum of this material has two main emission bands, namely, the blue and green bands. The first glow peak emits predominantly in blue region, whereas the second glow peak in the green region.     

Determination of kinetic parameters of thermally stimulated luminescence of Cu-doped BaSO4

Studies of thermally stimulated luminescence (TSL) of doped BaSO₄ with Cu activator have been carried out. The polycrystalline sample of Cu-doped BaSO₄ is prepared by recrystallisation method. The characterization and elemental analysis of BaSO₄:Cu compound are carried out by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The compound has orthorhombic structure at room temperature. The TSL studies of Cu-doped BaSO₄ sample show two glow peaks at 160 and 227 °C. Comparison of TL intensity of the most intensive glow peak of Cu- and Mn-doped BaSO₄ compounds with that of undoped BaSO₄ shows that addition of Cu and Mn impurity in BaSO₄ compound enhances the TL intensity by about 9 and 3 times, respectively. Among the studied samples, namely undoped, Cu- and Mn-doped BaSO₄, Cu-doped BaSO₄ is found to be the most sensitive. The trap parameters namely order of kinetics (b), activation energy (E), frequency factor (s) and Balarin parameter (γ) associated with the most intensive glow peak, i.e. the 227 °C glow peak of BaSO₄:Cu phosphor were determined by using isothermal decay method and glow curve shape (Chen's) method and these parameters are in good agreement.     

Analytical Expressions for the Mixed-Order Kinetics Parameters of TL Glow Peaks Based on the two Heating Rates Method

The two heating rates method (originally developed for first-order glow peaks) was used for the first time to evaluate the activation energy (E) from glow peaks obeying mixed-order (MO) kinetics. The derived expression for E has an insignificant additional term (on the scale of a few meV) when compared with the first-order case. Hence, the original expression for E using the two heating rates method can be used with excellent accuracy in the case of MO glow peaks. In addition, we derived a simple analytical expression for the MO parameter. The present procedure has the advantage that the MO parameter can now be evaluated using analytical expression instead of using the graphical representation between the geometrical factor and the MO parameter as given by the existing peak shape methods. The applicability of the derived expressions for real samples was demonstrated for the glow curve of Li₂B₄O₇:Mn single crystal. The obtained parameters compare very well with those obtained by glow curve fitting and with the available published data.     

Thermoluminescence,photoluminescence and EPR studies on Mn2+ activated yttrium aluminate (YAlO3) perovskite

Thermoluminescence (TL) measurements were carried out on undoped and Mn²⁺ doped (0.1 mol%) yttrium aluminate (YAlO₃) nanopowders using gamma irradiation in the dose range 1–5 kGy. These phosphors have been prepared at furnace temperatures as low as 400 °C by using the combustion route. Powder X-ray diffraction confirms the orthorhombic phase. SEM micrographs show that the powders are spherical in shape, porous with fused state and the size of the particles appeared to be in the range 50–150 nm. Electron Paramagnetic Resonance (EPR) studies reveal that Mn ions occupy the yttrium site and the valency of manganese remains as Mn²⁺. The photoluminescence spectrum shows a typical orange-to-red emission at 595 nm and suggests that Mn²⁺ ions are in strong crystalline environment. It is observed that TL intensity increases with gamma dose in both undoped and Mn doped samples. Four shouldered TL peaks at 126, 240, 288 and 350 °C along with relatively resolved glow peak at 180 °C were observed in undoped sample. However, the Mn doped samples show a shouldered peak at 115 °C along with two well defined peaks at ～215 and 275 °C. It is observed that TL glow peaks were shifted in Mn doped samples. The kinetic parameters namely activation energy (E), order of kinetics (b), frequency factor (s) of undoped, and Mn doped samples were determined at different gamma doses using the Chens glow peak shape method and the results are discussed in detail.     

A Modification of the Kinetic Equations Used for Describing the Thermoluminescence Phenomenon

In the present work we discussed the validity of the traditional first-, second- and general-order kinetic equations used to describe the thermoluminescence (TL) phenomenon. These equations were written in their present forms to explain the TL glow peaks at constant value of the heating rate. However, a widespread mistake was found when one uses these equations to explain the TL at different heating rates. This mistake is a result of unreal definition of the rate of change of trapped carriers as a function of temperature. A modification of the above-mentioned equations has been considered during this work to define correctly the TL phenomenon. As a result of this modification some characteristics of the TL glow peaks, namely, the TL intensity and the total integral will be changed. Following to the present work, an emendation of Chen–Winer method used to determine the activation energy of TL glow peak was considered during this work. Also, a modification of the equation used to determine the relative value of initial concentration of the trapped carriers was considered during this work.     

Radiation damage in single crystal L-Histidine as studied by low-temperature thermoluminescence techniques

X-irradiation of single crystal L-Histidine at 10 K produces TL glow peaks at 38, 72, 84, 122, 162, 204, and 245 K. The 84 K peak is the most intense one and is characterized by a thermal activation energy of 0.073 eV and frequency factor of 1.1×10³s^-1. Moreover, it is readily photobleachable, whereas the other glow peaks are not, and is tentatively correlated with the thermal decay of a carboxyl anion radical. Computer simulation of the Randall-Wilkins first-order TL expression provided a check on the experimentally derived parameters characterizing the 38 and 84 K peaks. The initial-rise method did not produce accurate parameters for the 38 K peak; however, computer simulation yielded an activation energy of 0.022 eV and a frequency factor of 20 s^-1 which were in agreement with the experimental shape of the glow curve. This TL peak is attributed to the thermal destruction of an imidazole cation radical. Emission spectra measurements of the 84 K luminescence (other peaks were of insufficient intensity) indicated that TL results from thermal release of electrons and their subsequent de-excitation to the ground state via the singlet and triplet manifolds. At sufficiently high temperatures (～78 K) one only observes singlet state emission due to intersystem crossing.     

Excitation of thermoluminescence in Eu doped Ba0.12Sr0.88SO4 nanophosphor by low energy argon ions

In the present paper thermoluminescence properties of argon ions irradiated barium strontium mixed sulphate phosphor are reported. The Ba_0.12Sr_0.88SO₄ phosphor was prepared by chemical co-precipitation method. The X-ray diffraction study of prepared sample suggests orthorhombic structure with average grain size of 37 nm. The samples were irradiated with 1.2 MeV Argon ions at fluences varying between 10¹¹-10¹⁵ ions/cm². The argon ions penetrate to the depth of 1.89 μm and lose their energy mainly via electronic stopping. Due to ion irradiation, a large number of defects in the sample are formed. Thermoluminescence (TL) glow curves were recorded for each of the ion fluence. These curves exhibit one broad peak with maximum intensity at 498 K composed of three overlapping peaks. This indicates that different sets of traps are being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The peaks were observed due to formation of trap levels by ion irradiation and subsequently activation of traps on thermal stimulation. The TL response of the nanophosphor is linear in the dose range 59 kGy-590 MGy. Kinetic parameters associated with the prominent peaks were calculated using glow curve deconvolution (GCD) and verified by different glow curve shape and sample heating rate methods.     

Kinetic analysis of high temperature secondary thermoluminescence glow peaks in α-Al2O3:C

The kinetic analysis of secondary glow peaks in carbon-doped aluminium oxide is reported. A glow curve measured at 0.4 °C s⁻¹ after beta irradiation to 3 Gy revealed at least five peaks as a result of various techniques of glow curve resolution; the dominant peak at 156 °C (peak II) and two weaker-intensity secondary peaks one at 36 °C (peak I) and the other at 264 °C (peak III). Peaks IIA and IV at 170 and 422 °C respectively only became apparent after removal of preceding more prominent peaks. The secondary peaks are particularly weak in intensity and are as usual dominated by the main dosimetry peak. The analysis in this report focusses on peak III, usually seen adjacent to the main dosimetry peak but whose presence is masked by the extreme sensitivity of the latter. Complementary analyses of the weaker intensity peaks I, IIA and IV are included. Peaks I, IIA and III are subject to first-order kinetics while for peaks II and IV the issue is less conclusive. The activation energy increases from 0.72 eV for peak I to about 1.3 eV for peak IV with values for peak II and IIA similar at ∼1 eV. In general, the frequency factor corresponding to the lower temperature peaks (I, II, and IIA) have values (10¹⁰–10¹² s⁻¹) that are an order of magnitude or so greater than for peaks III and IV (10⁹–10¹¹ s⁻¹). Except for peak I, peak II and all other secondary peaks are affected by thermal quenching whose activation energy was determined as ΔE = 0.95 ± 0.04 eV using peak IIA and as ΔE = 1.48 ± 0.10 eV using peak III. The overall conclusion is that all peaks correspond to electron traps and are associated with the same recombination centre.     

Determination of trapping parameters of dosimetric thermoluminescent glow peak of lithium triborate (LiB3O5) activated by aluminum

Lithium triborate (LBO) is a newly developed ideal nonlinear optical (NLO) crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. The effective atomic number (Z_eff=7.3) makes it a tissue equivalent material and this encourages studies on its thermoluminescence (TL) properties for a radiation dosimetry. The previous studies have shown that Al-doped LiB₃O₅ is a promising thermoluminescent dosimetric (TLD) material for dosimetric purposes and continuous and systematic investigations to improve its quality to get ones suited for dosimeter applications are worthy. In the given study, the additive dose (AD), initial rise with partial cleaning (IR), variable heating rate (VHR), peak shape (PS), three-points method (TPM) and computerized glow deconvolution (CGCD) methods were used to determine the kinetic parameters, namely the order of kinetics (b), activation energy (E_a) and the frequency factor (s) associated with the dosimetric thermoluminescent glow peak (P3) of Al-doped LiB₃O₅ after different dose levels with β-irradiation.     

Argon ions induced thermoluminescence properties of Ba0.12Sr0.88SO4 phosphor

Thermoluminescence properties of barium strontium mixed sulfate have been studied by irradiation with Argon ions. The sample was recrystallized by chemical co-precipitation techniques using H₂SO₄. The X-ray diffraction study of prepared sample suggests the orthorhombic structure with average grain size of 60 nm. The samples were irradiated with 1.2 MeV Argon ions at fluences varying between 10¹¹ and 10¹⁵ ions/cm². The argon ions penetrate to the depth of 1.89 μm and lose their energy mainly via electronic stopping. Due to ion irradiation, a large number of defects in the sample are formed. Thermally stimulated luminescence (TSL) glow curves of ion irradiated Ba_0.12Sr_0.88SO₄ phosphor exhibit broad peak with maximum intensity at 495 K composed of four overlapping peaks. This indicates that different sets of traps are being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). Thermoluminescence (TL) glow curves were recorded for each of the ion fluences. A linear increase in intensity of TL glow peaks was found with the increase in ion dose from 59 kGy to 5.9 MGy. The kinetic parameters associated with the prominent glow peaks were calculated using glow curve deconvolution (GCD), different glow curve shape and sample heating rate methods.     

Thermoluminescence and electron spin resonance after room-temperature X-ray irradiation of NaCl:Mn2+

A parallel investigation of thermoluminescence (TL) and electron spin resonance (ESR) spectra on room-temperature (RT) X-irradiated NaCl:Mn²⁺ has been performed. The TL spectra in the range 20–300°C consist of five glow peaks, numbered from I to V. Temperatures at maximum height are 41°, 68°, 118°, 152° and 216°C, respectively. Peaks I, II and IV obey first-order kinetics, whereas peaks III and V fit second-order behavior. The wavelength spectrum for all glow peaks consists of two bands centered at 595 and 400 nm. The 595 nm emission is attributed to hole capture by Mn⁺ and subsequent deexcitation of Mn²⁺. The 400 nm emission is produced as a consequence of hole-F center recombination.The correlation of TL glow peaks to various defects has been investigated. Peak II is clearly related to manganese-vacancy dipoles and peak I can be roughly associated to free cation vacancies. Peak IV appears to relate to large Mn-aggregates, whereas peak V is intrinsic and not related to impurities.On the other hand, ESR data indicate that each glow peak in the 595 nm emission is associated to the annihilation of a given Mn-center; Peak I to Mn⁰C, peak II to Mn⁰C and Mn⁺, peak III to Mn⁺ and peaks IV and V to Mn⁰-D.     

An improved experimental procedure of separating a composite thermoluminescence glow curve into its components

We present an improved experimental procedure of separating a composite thermoluminescence glow curve into its components. Careful monitoring of the isothermal cleaning process using the initial rise method ensures the complete thermal removal of TL peaks. Digital subtraction of two experimental TL glow curves yields individual experimental TL glow peaks. Several standard methods (initial rise and whole glow curve) are used to obtain the energy values and frequency factors of the traps. The method has been used successfully to analyze the well-known composite TL glow curve of the dosimetric material LiF (TLD-100). The limitations of the method are illustrated by analyzing the highly complex TL glow curve of a UV irradiated synthetic calcite consisting of at least 6 TL peaks. Although the method works best for TL glow curves described by first order kinetics, it should also be applicable to more general kinetics.     

Reconstruction of thermally quenched glow curves in quartz

The experimentally measured thermoluminescence (TL) glow curves of quartz samples are influenced by the presence of the thermal quenching effect, which involves a variation of the luminescence efficiency as a function of temperature. The real shape of the thermally unquenched TL glow curves is completely unknown. In the present work an attempt is made to reconstruct these unquenched glow curves from the quenched experimental data, and for two different types of quartz samples. The reconstruction is based on the values of the thermal quenching parameter W (activation energy) and C (a dimensionless constant), which are known from recent experimental work on these two samples. A computerized glow-curve deconvolution (CGCD) analysis was performed twice for both the reconstructed and the experimental TL glow curves. Special attention was paid to check for consistency between the results of these two independent CGCD analyses. The investigation showed that the reconstruction attempt was successful, and it is concluded that the analysis of reconstructed TL glow curves can provide improved values of the kinetic parameters E, s for the glow peaks of quartz. This also leads to a better evaluation of the half-lives of electron trapping levels used for dosimetry and luminescence dating.     

Luminescence and evaluation of trapping parameters in NaMgSO4Cl: X (X=Cu or Ce) phosphor

Thermoluminescence (TL) characteristics of recently developed high sensitive mixed halosulphate phosphors, NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce were studied in comparison with CaSO₄: Dy in order to assess the possibility of their use in personal monitoring and TLD phosphors at very low dose of 5 Gy. It was found that NaMgSO₄Cl: Cu is 5.59 times and NaMgSO₄Cl: Ce is 6.18 times more sensitive as compared to standard CaSO₄: Dy. UV photo-excited luminescence from Cu to Ce doped NaMgSO₄Cl halosulphate phosphors has been investigated. The intense emission of the spectrum is assigned to electronic transitions 3d⁹4s¹→3d¹⁰ in monovalent copper ion and 5d→4f in Ce³⁺ ions. Increase in PL peak intensity suggesting that Cu and Ce play an important role in PL emission in the present matrix. These phosphors were synthesized by the wet chemical method. XRD, photoluminescence (PL) and thermoluminescence (TL) characterization of phosphors has been reported in this paper. The preparation of an inexpensive and high sensitive NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce with TL glow peaks for different concentrations are observed between 160 and 195 °C and between 200 and 225 °C, respectively, exposed to gamma-rays of ⁶⁰Co for their thermoluminescence (TL) properties. The glow curves have been recorded at a heating rate of 2 K s^?1 and irradiated at a dose rate of 0.995 kGy h^?1 for 5 Gy. In present study the trapping parameters such as order of kinetics (b), activation energy (E) and frequency factors (s) have been calculated for the 195 and 200 °C glow peaks of NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce, respectively by using Chen's method. The paper discusses the luminescence of Cu⁺ and Ce³⁺ by simple method of incorporation in NaMgSO₄Cl host.     

Thermally stimulated luminescence studies of undoped,Cu- and Mn-doped CaSO4 compounds

Thermally stimulated luminescence (TSL) of undoped and doped CaSO₄ with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaSO₄ are prepared by the melting method. The formation of CaSO₄ compound is confirmed by X-ray diffraction and Fourier transform infrared studies. Scanning electron microscopic studies of CaSO₄ are also carried out.

The TSL glow curves of undoped CaSO₄, Cu- and Mn-doped CaSO₄ are studied. Comparison of the thermoluminescence (TL) intensity of the most intensive glow peak of Cu-doped CaSO₄ compound with that of undoped CaSO₄ shows that addition of Cu impurity in CaSO₄ compound enhances the TL intensity by about four times. However, the addition of Mn impurity to undoped CaSO₄ increases the TL intensity by about three times when compared with that of undoped CaSO₄. The TL-dose dependence of all three samples was studied and was observed to be almost linear in the studied range of irradiation time. Among the samples studied, namely undoped CaSO₄ and Cu- and Mn-doped CaSO₄, Cu-doped CaSO₄ is found to be the most sensitive. The trap parameters, namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the most intensive glow peaks of CaSO₄:Mn, CaSO₄:Cu and CaSO₄ phosphors were determined using the glow curve shape (Chen's) method.