In this paper we describe the thermoluminescence (TL) characteristics of ZnB2O4:Pr3+ phosphors with Pr concentrations varying between 0.2 and 1 mol% prepared by a wet-chemical method. The TL glow ...curves of the phosphor sample consisted of three peaks located at 71 °C (P1), 124 °C (P2) and 233 °C (P3). The TL intensity increased with the beta dose ranging from ∼0.1 to ∼20 Gy. Dose response, reproducibility and trapping parameters of TL glow curves were evaluated to clearly reveal thermoluminescence features. We observed that TL intensity of P2 and P3 peaks decreases as the heating rate increases. Trap parameters were estimated via the Hoogenstraaten, Booth-Bohun-Parfianovitch, the initial rise methods combined with Tm−Tstop experiment and TLanal CGCD program. Heating rates were varied to use in the Hoogenstraaten analyses. The Tm−Tstop investigations on regenerated TL signals for P1 and P2 peaks indicated that ZnB2O4:Pr3+ phosphor has four electron trap levels with energy values in the range of 0.5–1.5 eV These four traps have first order kinetic and are formed at high temperature region. Resulting values are utilized as a reference for the CGCD procedure and the trapping parameters from the TL glow curves are calculated. The figure of merit (FOM) of the TL glow curve during curve fitting procedures is found to be 2.019%. The intensities of the main dosimetric peaks appeared at 124 °C and 233 °C exhibits good linear dose response up to 20 Gy. These results provide valuable knowledge for use of the characteristics of Pr doped ZnB2O4 in dosimetry research, just need to eliminate low temperature TL peak.
•ZnB2O4:Pr3+ phosphors were prepared by a wet chemical method.•The TL glow curves of the samples were analysed.•IR combined with Tm−Tstop,TLanalandCGCDwereusedtocalculate the trap parameters.•The dose-response was between 0.11 and 20.24 Gy under beta radiation.
A series of MoO3:Dy3+ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The ...prepared samples were characterized through XRD measurements and exhibited that Dy3+ ions can be successfully incorporated into the host material. The PL emission bands of Dy3+ doped MoO3 were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2, respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy3+ ions were incorporated into MoO3 host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching.
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•MoO3 phosphors doped with Dy were synthesized by a gel-combustion method.•Photoluminescence of undoped, and Dy doped MoO3 phosphors are reported.•Concentration quenching was suppressed.
Lantanium triborate (LaB3O6) samples doped with Eu3+ ions are synthesized via combustion route. This study primarily reports the thermoluminescence (TL) behaviour of LaB3O6 host. X-ray diffraction ...(XRD) pattern reveals that LaB3O6 exhibits a single phase matched with JCPDS card 98-002-3609. Dose response, reusability and trap parameters of TL glow curves are evaluated to clearly reveal the TL features. The results show that the peak positions of TL glow curves are affected by varying the concentration of Eu. The experimental results obtained from the dose-response of LaB3O6:Eu3+ (1%) which has given high TL intensity reveal that the intensity of TL given by the total area under glow curves shows a good linearity (b= 0.997) up to 20 Gy. In addition, the minimum detectable dose (MDD) value has been calculated as 1.45 mGy with a standard deviation of 0.8%. Main TL peak maxima is observed around 197 °C with heating rate (HR) of 2 °Cs−1. An anomalous HR effect is observed for this peak in the range of 0.5–20 °Cs−1 with beta dose of 5 Gy. To find the overlapping peak numbers and determine the kinetic parameters of the main peak of LaB3O6:Eu3+ (1%), Initial Rise (IR) method using Tm−Tstop experiment and CGCD analysis have been performed for HRs of 0.5 and 2 °Cs−1. It can be said that the results of the methods are in good agreement when same trap numbers (at least eight separate peaks for both) and close energy values are taken into consideration. Deconvolution procedure of LaB3O6: Eu3+(1%) is performed using general order kinetic equation by R studio ‘tgcd’. Additionally, the lifetimes of each deconvolved peaks by CGCD of Eu activated LaB3O6 (1%) have been calculated. Based on the results it can be put forth that TL characteristics of Eu doped LaB3O6 can be used as a promising material for thermoluminescence dosimetry-environmental applications.
•LaB3O6 phosphors doped with Eu synthesized by a combustion method.•TL glow curve recorded under beta excitation.•TL glow curve contains a single peak at 197 °C.•Anomalous heating rate was observed.•Phosphor exhibits dosimetric TL glow peak.
Here we report a detailed structural analysis, and properties of the cathodoluminescence (CL), photoluminescence (PL) and 3D thermoluminescence spectra of the Tm3+ incorporated ZnB2O4 phosphor ...successfully synthesized through wet-chemical synthesis. The formation of a single-phase compound is verified through X-ray diffraction (XRD) studies. The phosphor shows an efficient blue emission located at 458 nm corresponding to 1D2→3F4 under both a low voltage electron beam and UV excitation. The optimal concentration of the doped Tm3+ is 0.5 mol% in CL and PL measurements. The corresponding concentration quenching mechanism is confirmed to be a multipole-multipole interaction, and the critical distance between Tm3+ ions is estimated to be 34 Å. Incorporating Li+ remarkably enhances the luminescence intensity probably because of the charge compensation effect. Li ions are speculated to fill the defects in the ZnB2O4 host and then the excitation energy transfers from the host to Tm3+. Surprisingly, the thermoluminescence spectra of ZnB2O4:Tm3+ and Li+ co-doped ZnB2O4:Tm3+ recorded in the temperature range 30–400 °C follow a different pattern compared with PL and CL data. The dominant signals come from Tm3+ sites. Above room temperature, the Tm3+ ions do not show the peak temperature movement, but do exhibit a different pattern with the addition of co-doped Li+ ions. These results indicate that these phosphors are promising candidates for luminescence-based optoelectronic devices.
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•Li co-doped ZnB2O4:Tm3+ phosphors were synthesized by wet chemical method.•Structural and luminescence properties were conducted by XRD, PL, CL and 3DTL.•Luminescence enhancement was realized by charge compensation.•The effects of temperature on Tm and Li co-doped luminescence properties were also discussed.
This study examines the thermoluminescent (TL) properties of undoped Ca4YO(BO3)3 phosphor, focusing on how it behaves under a variety of experimental conditions. The IRSL-TL 565 nm was chosen as the ...appropriate detection filter among various optical detection filter combinations. During the preheating trials conducted at a rate of 2 °C/s, the TL peak exhibited increased intensity, particularly around 200 °C. The experimental outcomes demonstrated a reliable linear relationship (R2 = 0.996 and b = 1.015) in the dose response of undoped preheated Ca4YO(BO3)3 within the range of 1–200 Gy. The investigation encompasses a range of techniques, including the TM-Tstop method, computerized glow curve deconvolution (CGCD) analysis, and theoretical modelling. The application of the TM-Tstop method to samples irradiated with a 5 Gy dose revealed distinct zones on the TM versus Tstop diagram, signifying the presence of at least two discernible components within the TL glow curve, specifically, a single general order kinetics peak and a continuous distribution. The analysis of activation energy versus preheated temperature exhibited a stepwise curve, indicating five trap levels with depths ranging between 1.13 eV and 1.40 eV. The CGCD method also revealed the superposition of at least five distinct TL glow peaks. It was observed that their activation energies were consistent with the Tm-Tstop experiment. Furthermore, the low Figure of Merit (FOM) value of 1.18% indicates high reliability in the goodness-of-fit measure. These findings affirm the reliability and effectiveness of the employed methods in characterizing the TL properties of the Ca4YO(BO3)3 phosphor under investigation. Theoretical models, including the semi-localized transition model, were introduced to explain anomalous observations in TL glow peak intensities and heating rate patterns. While providing a conceptual framework, these models may require adjustments to accurately capture the specific characteristics uncovered through CGCD analysis. As a potential application, the study suggests that the characterized TL properties of Ca4YO(BO3)3 phosphor could be utilized in dosimetric applications, such as radiation dose measurements, owing to its reliable linear response within a broad dose range.
•Ca4YO(BO3)3 nanophosphors were produced using the combustion method.•Trap levels were found to be between 1.13 eV and 1.40 eV.•A reliable linear relationship was established between 1 Gy and 200 Gy.•The TM-Tstop method and computerized glow curve deconvolution (CGCD) analysis were utilized for analysis.
Thermoluminescence of β-particle induced Bern-4M muscovite Portakal-Uçar, Z.G.; Akca, S.; Balci-Yegen, S. ...
Radiation physics and chemistry (Oxford, England : 1993),
September 2020, 2020-09-00, 20200901, Letnik:
174
Journal Article
Recenzirano
Bern-4M muscovite from Switzerland was investigated via X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and thermoluminescence (TL). Muscovite has the theoretical formula ...KAl2(AlSi3O10)(FOH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). Chemical analysis of the muscovite sample was carried out using EDS for major oxides. The results indicate that muscovite includes oxygen (59.1%), silicon (18.86%), and aluminum (15.22%) as major elements and contains low concentrations of potassium, magnesium, and sodium. In standard muscovites potassium use to be 10% and oxygen 47%, probably the sample was strongly lixiviated before the analysis. The thermoluminescence spectrum exhibits a wide glow peak located at 250 °C with a shoulder peak at high temperature region. Trap depth and frequency factor were calculated using Hoogenstraaten's method and found to be 1.16 eV and 1.4 × 1010 s−1, respectively. Reproducibility test indicated that the values within ±5% were obtained after 15 cycles. The storage time experiments were performed for different time periods up to 1 week for dark fading.
•Natural Bern-4M muscovite were investigated by XRD, EDS and TL.•The sample shows an intense wide band around 240 °C.•Trap depth and frequency factor were estimated via Hoogenstraaten's method.
Although thrombocytopenia in the intensive care unit (ICU) is associated with a poorer outcome, the precise relationship between the time course of platelet counts and the mortality rate has not been ...well defined.
To describe the time course of the platelet count in relation to the mortality rate in critically ill patients.
Substudy of a prospective, multicenter, observational cohort analysis.
Forty ICUs in 16 countries from Europe, America, and Australia.
Data were collected from all ICU admissions in a 1-month period, excluding patients younger than 12 yrs old and those who stayed in the ICU for <48 hrs after uncomplicated surgery. A total of 1,449 critically ill patients were enrolled, including 257 who stayed in the ICU for >2 wks.
None.
Platelet counts were collected daily throughout the ICU stay, together with other measures of organ dysfunction. Thrombocytopenia was defined as a platelet count of <150 x 103/mm3. A relative increase in platelet count was defined as a 25% increase above the admission value, together with an absolute platelet count of > or =150 x 103/mm3.
For the entire population, the platelet count was lower in the 313 nonsurvivors than in the 1,131 survivors throughout the ICU course. Of the 257 patients who stayed in the ICU for >2 wks, 187 (64%) survived. The platelet count decreased significantly in the first days after admission to reach a nadir on day 4 in both survivors and nonsurvivors. In the survivors, the platelet count returned to the admission value by the end of the first week and continued to rise to become significantly greater than the admission value by day 9. In the nonsurvivors, the platelet count also returned to the admission value after 1 wk, but there was no subsequent increase in platelet count. A total of 138 (54%) patients had thrombocytopenia on day 4, and these patients had a greater mortality rate than the other patients (33% vs. 16%; p <.05). On day 14, 51 (20%) patients had thrombocytopenia, and these patients had a greater mortality rate than the other patients (66% vs. 16%; p <.05). Thrombocytopenia was less common on day 14 than on day 4 (20% vs. 54%; p <.05), but the mortality rate was greater in the thrombocytopenic patients on day 14 than those who were thrombocytopenic on day 4 (66% vs. 33%; p <.05). The ICU mortality rate of nonthrombocytopenic patients on day 14 was also significantly lower in patients with, than without, a relative increase in platelet count on day 14 (11% vs. 30%; p <.05).
Platelet count changes in the critically ill have a biphasic pattern that is different in survivors and nonsurvivors. Late thrombocytopenia is more predictive of death than early thrombocytopenia. A relative increase in platelet count after thrombocytopenia was present in survivors but not in nonsurvivors. Although a single measured platelet count is of little value for predicting outcome, changes in platelet count over time are related to patient outcome.
In this study, we have synthesized CaF2:Nd3+,Ce3+ phosphors by solid state reaction method. The thermoluminescence (TL) properties of the family of synthesized phosphors (CaF2:Ce3+ and ...CaF2:Ce3+,Nd3+) were investigated using a combination of a SCHOTT BG39 and HC414/46 filters. This gave the highest TL intensity of each phosphor after 10 Gy β-irradiation. Two TL glow peaks of CaF2:Nd3+,Ce3+ phosphor are centered at around 90 and 265 °C (with a heating rate of 2 °Cs−1). The glow peaks displayed a linear dose response in the range of 0.1–50 Gy. Various heating rates (VHR) were performed between 0.5 and 10 °Cs−1. It was seen that the TL intensity at 90 °C decreases and peak maximum temperature shifts to higher temperatures with an increasing heating rate. The TL intensity of the glow peak located at 265 °C increases with heating rate. The initial rise (IR) applied after TM–Tstop experiment and computerized glow curve deconvolution (CGCD) methods in addition to the VHR method on the glow curves of CaF2:Nd3+,Ce3+ phosphor were used to determine the number of peaks, the order of kinetics (b), activation energy (E) and frequency factor (s). The response of TL glow curves remained constant within ±2% deviation from the initial value after 10 cycles of reuse.
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•Undoped, Ce and Nd doped CaF2 phosphors were successfully prepared via solid state reaction method.•Thermoluminescence properties of Ce and Nd doped CaF2 phosphors are reported.•Unusual heating rate dependence was observed on CaF2:Nd3+,Ce3+.•Kinetic parameters were calculated different methods.
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