TL Emission Spectra Research Articles

Study of the centers responsible for the TL emission by EPR and PL analysis of Eu-doped CaSiO3 phosphors synthesized by the devitrification method

CaSiO3 doped at different ppm of Eu were synthesized by the devitrification method. Polycrystals exhibit a prominent high-temperature TL peak that increases in intensity and shifts toward higher temperatures with increasing amounts of dopant. TL emission spectrum of CaSiO3: Eu displays two very broad bands centered at 400 and 440 nm corresponding to the temperatures of 229.5 and 373.5 °C, respectively. PL measurements indicate the presence of Eu2+ and Eu3+ ions. EPR spectrum arises from two defect centers. One of the centers with principal g-values 2.016, 2.0091, and 2.0051 is attributed to O− ion and the center correlates with the TL peak at 236 °C. Center II with an isotropic g-value of 2.0018 is attributed to an F+ center and the center relates to the TL peak at 120 °C. Center III is also tentatively identified as the F+ center which is associated with the TL peak at 365 °C.

Structural and optical properties of Magnesium borate phosphors for dosimetric purpose

The recent study presented the structural and optical features of Sm-doped magnesium borate. The X-ray diffraction pattern displays the crystal structure of the prepared sample which matches with the JCPDS card. The morphological studies, elemental analysis, and vibrational properties were examined by SEM, EDX, and FTIR measurements. The TL emission spectra of pure magnesium borate phosphors show only one peak at 209°c, and doped phosphors show an intense peak at 212°c. The PL excitation (PLE) spectrum of the MgB4O7: Sm samples was observed at a wavelength range of 330 – 475 nm. The maximum sharp line is detected nearly at 407 nm that corresponds to ions Sm3+ transition of 6H5/2 → 4K11/2 and the PL emission of the intense line was measured at a wavelength of 612 nm due to the significant excitation of Sm3+ ions from 4G5/2 to 6H7/2. In addition, the bonding behavior of synthesized phosphors was determined by Raman spectroscopy.

Luminescence properties of a novel cyan-blue light emitting Ce3+doped SrZrSi2O7 phosphor

A novel Ce3+ doped SrZrSi2O7 (SZSO) phosphor with different doping concentration (0.05–1.5 mol %) were synthesized by conventional solid-state reaction method. To confirm crystal structure and phase purity of prepared phosphor X-ray diffractions (XRDs) have been done. Surface morphology, compositional and functional groups analysis were investigated using FE-SEM, EDXS & FTIR techniques. In order to study the optical properties of the synthesized phosphor photoluminescence and thermoluminescence were investigated in detailed. Photoluminescence studies of SZSO: Ce3+ phosphor shows strong broad excitation peak at 293 nm owing due to 4f → 5d transition and corresponding broad emission peak obtain at 480 nm due to 5d → 4f spin allowed transition. The optimum PL intensity obtain for 0.1 mol% Ce3+ doping concentration. CIE co-ordinate, color purity and CCT of prepared phosphor are also calculated which shows the SZSO: Ce3+ phosphor emits cyan-blue light, can be applicable for solid state lighting. Thermoluminescence of SZSO: Ce3+ phosphor shows two TL glow curve peaks at 56 °C and 130 °C temperature. The optimum TL intensity obtained for 0.2 mol% Ce3+ doped SZSO phosphor for 15 min UV irradiation time at 254 nm UV excitation source. TL emission spectra and fading effect are also analyzed. TL kinetic parameters are determined by peak shape method. Thermoluminescence properties shows that prepared SZSO: Ce3+ phosphor will be potential applicable for UV-dosimetry.

UV light induced processes in pure and doped AlN ceramics

AlN ceramics samples, pure and doped with Y 2 O 3 , Eu 2 O 3 and GaN, and produced from the same AlN powder, were studied for photoelectric effect, photoluminescence spectra and kinetics and thermoluminescence under irradiation with UV light from above- and below-bandgap spectral region. Common properties of all studied samples were found, such as presence of the complex UV-Blue and Red emission bands in PL and TL emission due to oxygen-related defects and manganese impurities, correspondingly; a new emission band at 320 nm, which is present in PL and absent in TL emission spectrum and is assigned to an oxygen-related centre; luminescence decay comprised of superposition of exponents of various duration from nanoseconds to hundreds of minutes. Among the studied samples the dopant-related luminescence was observed only in AlN:Eu 2 O 3 at 525 nm. No effect of the dopants on fading rate of the stored TL signal was observed. Such properties of the PL and TL as luminescence intensity and relative contribution of the emission bands manifested by individual samples were explained by influence of the dopant type and ceramics sintering procedure on generation and recharging of the intrinsic and impurity defects. • Pure and doped AlN ceramics show a photoelectric effect under UV light from the above- and below-bandgap spectral regions. • Luminescence spectra of all samples contain 400, 480 and 600 nm bands, in AlN:Eu additional 525 nm band is observed. • In all samples a novel luminescence band is found at 320 nm, preliminary ascribed to (V Al -2O N ) 0 centres. • Photoluminescence kinetics is characterized by superposition of exponents varied from nanoseconds to hundreds of minutes. • Sintering procedure and doping of AlN ceramics affect generation of the oxygen-related centres and charging state of defects.

Thermoluminescence Response of AlN+Y2O3 Ceramics to Sunlight and X-Ray Irradiation

Abstract AlN is a wide band gap material with promising properties for dosimetric applications, especially in UV dosimetry. In the present research, the thermoluminescence method is used in order to better understand sunlight and X-ray irradiation effects on yttria doped AlN ceramics. In general, the TL response is characterised by a broad TL peak with maxima around 400–450 K and a TL emission spectrum with UV (400 nm), Blue (480 nm) and Red (600 nm) bands. Compared to the X-ray irradiation, sunlight irradiation creates a wider TL glow curve peak with a maximum shifted to higher temperatures by 50 K. Furthermore, in the TL emission spectra of AlN irradiated with sunlight the UV band is suppressed. The reasons of the TL peculiarities under two types of irradiation are discussed. Practical application of AlN ceramics as material for UV light TL dosimetry and, in particular, for sunlight dosimetry is estimated.

Photoluminescence and comparative thermoluminescence studies of UV/γ-irradiated Dy3+ doped bismuth silicate phosphor

A series of Bi4Si3O12:Dy3+ phosphor have been synthesized via conventional solid-state reaction method and its luminescence properties were investigated as near cool white light emitting and long afterglow phosphor. Crystal structure and phase structure characterization is determined using X-ray diffraction (XRD), SEM and EDS. Rietveld structural refinement and XRD confirms that prepared sample exhibit pure cubic structure [space group I-43d]. Photoluminescence spectra of both doped and undoped Bi4Si3O12 phosphor were efficiently excited in the range of 200-450 nm, and prepared phosphor under 272 nm excitation exhibit three emission peaks located at 463 nm(blue), 482 nm(blue) and 576 nm (yellow) corresponding to 3P1 → 1S0, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions. Characteristic emission peaks of Dy3+ centered at 482 nm and 576 nm were assigned for white light emission. The calculated Commission Internationale de I’Eclairage (CIE) chromaticity confirms that with Dy3+ doping, the luminescence co-ordinates of Bi4Si3O12 phosphor shift to near white(x = 0.316, y = 0.358) region which is close to commercial pc-LED (Blue LED + YAG:Ce3+) (x = 0.320, y = 0.320) co-ordinates. Computation of correlated color temperature 6184 K endorses that prepared phosphor is cool in nature and can be served as white light emitting phosphor. Comparative thermoluminescence study of UV and γ-irradiated Bi4Si3O12:Dy3+ phosphor is performed for the dosimetry application. TL intensity is recorded maximum at 30 min under UV irradiation (256 nm), and for γ irradiation, it was recorded at 10 kGy dose rate. γ-irradiated Bi4Si3O12:Dy3+ phosphor TL study is reported for the first time at different dose rate and concentration for high dosimetry application. The defect characteristic is examined, Trap depths and other kinetic parameters are also evaluated by Chen’s peak shape method. Decay and fading measurement under UV/γ irradiation are performed to examine the long after glow properties of prepared samples. TL emission spectrum studies are also performed.

Luminescent properties of undoped and Ce3+ doped crystals in Y2O3[sbnd]Lu2O3[sbnd] Al2O3 triple oxide system grown by micro-pulling-down method

Within this work, the undoped and Ce3+ doped Y2O3 – Al2O3 double system crystals were grown from the melt by micro-pulling-down method and their basic luminescent properties have been investigated. Luminescent properties of the obtained crystal samples were studied by cathodo- and thermo-luminescence methods (CL and TL, respectively). The TL spectra were measured after the samples irradiation with both beta and alpha particles. It was found that the obtained cerium doped crystals exhibit dominant emission bands with maxima at around 380 nm in the centers of crystals, and low-intensive satellite band peaked at 560 nm at the boundaries of crystals, what corresponds to the well-known perovskite and garnet phases, respectively. For YLu substituted crystals only the emission band of garnet phase was observed. It tends to suggest that even a small substitution of Y3+ by Lu3+ ions in the host lattice causes a strong suppression of the 380 nm luminescence of the perovskite phase. This was also confirmed by TL spectra measurements performed over the different spectral ranges. A good agreement of CL and TL emission spectra suggests that the same emission centers are involved in both processes. The obtained results showed that, besides of the well-known scintillating properties, the materials under study can be also considered as the energy storage phosphors for dosimetric applications.

Cool white light emission from Dy3+ activated alkaline alumino silicate phosphors.

A series of single phase white light emitting CaSrAl2SiO7:Dy3+ phosphors were prepared by traditional high temperature solid state reaction method. Structural characterization was done by X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy analyses. Optical characterization was performed from photoluminescence and thermoluminescence studies. When excited at 350 nm, CaSrAl2SiO7:Dy3+ phosphors showed two intense emission bands in the blue region (480 nm and 493 nm) corresponding to 4F9/2 → 6H15/2 transition and one in yellow region (576 nm) corresponding to 4F9/2 → 6H13/2 transition. The Commission Internationale de I'Eclairage diagram was drawn for entire series. It confirmed that by manipulating Dy3+ content the luminescence color of CaSrAl2SiO7:Dy3+ phosphors were tuned from blue to white region. Computation of correlated color temperature suggested that present phosphor was cool in appearance hence CaSrAl2SiO7:Dy3+ phosphor can serve as a white light emitting phosphor and may be useful in outdoor illumination. A detailed study on thermoluminescence of ultraviolet exposed samples was done and possible mechanism of thermoluminescence was discussed. TL emission spectrum was also measured.

Luminescence properties of near-UV excitable yellow-orange light emitting warm CaSrAl2SiO7:Sm3+ phosphors

Single-phase CaSrAl2SiO7:Sm3+ phosphors were synthesized by traditional high temperature solid state reaction method. Formation of samples and phase analysis were confirmed by X-ray diffraction technique. Morphology was done by field emission scanning electron microscopy and elemental compositions were confirmed by energy dispersive X-ray analysis. Present phosphors have tetragonal crystallography with space group P4¯21m. Average crystallite size was calculated by using Scherrer and Williamson-Hall method. Photoluminescence study of CaSrAl2SiO7:Sm3+ phosphor was investigated. Under different excitation wavelengths, PL spectra consist of four emission bands at 564, 570, 601 and 650 nm. The emission bands located at 564 and 570 nm are associated with the transition 4G5/2 → 6H5/2 while emission bands at 601 and 650 nm are due to 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2, respectively. Intense emission was obtained when phosphor was excited under 404 nm wavelength. Non-radiative energy transfer process involved in concentration quenching, was also discussed. CIE coordinate is found in yellow-orange region, hence CaSrAl2SiO7:Sm3+ phosphors emit yellow-orange light when efficiently excited by near UV (∼400 nm) LED chip. Color purity and CCT of the phosphor were determined; CCT suggests that present phosphor is a good candidate as a warm yellow-orange color emitting phosphor. Effect of different heating rates and different UV exposure time on the TL glow curve of the phosphor was investigated. Activation energies and kinetic parameters for different traps were calculated by using peak shape method. TL emission spectrum was also recorded. Present article explains all the possible mechanisms associated with luminescence process in CaSrAl2SiO7:Sm3+ phosphors.

Optical studies of the Ba1-XMgAl10O17:Eux phosphors synthesis by combustion route

In the present work BaMgAl10O17:Eu phosphors were prepared successfully using the combustion route by employing urea as a fuel. The structural and luminescent properties were measured. The surface areas of the phosphors were found ∼14.8 m2/g and the band gap was calculated ∼5.24 eV. The crystallite sizes of the synthesis phosphor were found in the order of ∼70 nm–650 nm. TL studies of the discussed phosphors were carried out under UV (254 nm) exposure. The efficient and more intensive TL glow curve was observed under 30-min dose of UV. The TL emission spectra of the Ba0.99MgAl10O17:Eu0.01 phosphor showed the characteristic Eu2+ emission peaks ∼443 nm, originating from the electronic transitions 4f65d1→4f7. The phosphors showed strong blue luminescence and 89% quantum efficiency for 8mol% of Eu. Persistence phenomena of the phosphors were discussed using both TL and PL decay properties.

Tuning of luminescent properties of Zn1-xMgAl10O17:Eux nano phosphor

The Zn1-xMgAl10O17:Eux2+ (x = 0.01–0.4) nano phosphors were prepared successfully using the combustion route by employing urea as a fuel. The structural, microstructural, thermal, optical and luminescent properties were measured on the samples. The nano phosphors were found to be of surface area (∼13.92 m2/g) and insulators of the band gap (∼5.24eV). Photoluminescence properties on the samples were characterized by excitation (λex. = 340 nm) and emission (λem. = 440 nm) spectra. The phosphors showed strong blue luminescence (440 nm-460 nm) as well as showed weak luminescence in 577 nm, 589 nm, 596 nm, and 615 nm in the orange-red region, which are attributed to 4f65 d1→4f7 and 5D0→7Fj (j = 0, 1,…) transitions of the Eu (II) and Eu (III) ions respectively. The tuning of this blue luminescent properties as compared to the earlier reported red luminescence has been achieved. Thermo-luminescence glow curve recorded under 10-minute dose of UV (254 nm) radiation have been used to calculate the kinetic parameters and the activation energy of the nano phosphors by using the Chens-equation. The TL emission spectra of the Zn0.99MgAl10O17:Eu0.01 phosphor showed the characteristic Eu2+ emission peaks ∼450 nm (blue) originating from the transitions 4f65 d1→4f7. The possible mechanism of the PL and TL of blue light emitting phosphor are also discussed.

Thermoluminescent dosimetric properties of CaF2:Tm produced by combustion synthesis

Abstract Calcium Fluoride is one of the oldest known thermoluminescent materials and is considered to be one of the most sensitive. This work presents the dosimetric properties results of CaF2:Tm produced by combustion synthesis. The X-ray diffraction confirmed that CaF2 was successfully produced. TL emission spectra, obtained using a Hammamatsu optical spectrometer, have the same lines of commercial CaF2:Tm, although transitions 3P0→3F4 (455 nm) and 1G4→3H6 (482 nm) are shown to be proportionally more intense. The deconvolution technique was employed and seven glow peaks were found similar to the commercial CaF2:Tm. A linear dose response curve was obtained for the range 0.1 mGy to 100 Gy, with the onset of a supralinear behavior at 50 Gy up to 100 Gy. The minimum measurable dose for gamma was around 100 μGy for a 6.0 mm diameter by 1.0 mm in thickness pellet. No significant fading was observed in 60 days of storage, within experimental uncertainties, showing that the main dosimetric peak is stable.

OSL, TL and IRSL emission spectra of sedimentary quartz and feldspar samples

This contribution presents a variety of different luminescence emission spectra from sedimentary feldspar and quartz samples under various stimulation modes. These are green stimulated quartz (OSL-) spectra, quartz TL spectra, feldspar IRSL and post-IR IRSL spectra. A focus was set at recording OSL and IRSL spectra at elevated stimulation temperatures such as routinely applied in luminescence dating. This was to test whether optical stimulation at elevated temperatures results in a shift of emission peaks. For OSL emissions of quartz, this has so far not been tested. In case of feldspar emissions, post-IR IRSL conditions, hence IRSL emissions at a low temperature, directly followed by high temperature post-IRSL emissions, are explicitly investigated. All spectra were recorded using a new system incorporated into a Lexsyg luminescence reader. Thus, this study, besides presenting new spectral data, also serves as a feasibility study for this new device. It is shown that (a) the new device is capable of automatically measuring different sorts of spectra, also at elevated temperatures, (b) known thermally and optically stimulated peak emissions of quartz and feldspar are confirmed, (c) obtained IRSL and OSL spectra indicate that there is no significant relation between peak emission and stimulation temperature.

Synthesis and thermoluminescent response of CaF2 doped with Tm3+

Doped Calcium fluoride (CaF2) is a well known dosimetric material used for measurement of ionizing radiation. In the literature we can find several synthetic routes to prepare this materials, however the majority of the methods present disadvantages such as long time for preparation, use of hazardous materials or crystal growth infrastructure. In order to overcome these problems, in this paper we present a simple wet chemical process by which calcium fluoride doped with thulium was fabricated. The crystal structure and particle size of the synthesized material was characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The thermoluminesce response for samples irradiated with 60Co gamma radiation showed a linear response up to 10 kGy. Additionally, the TL emission spectra shows spectroscopic emission lines characteristic of Tm3+, where the relative intensity of each line depend on the fabrication parameters.

Comparison of commercial thermoluminescent readers regarding high-dose high-temperature measurements

Three different thermoluminescent measuring systems have been compared with respect to the differences in temperature profiles, spectral sensitivities, as well as characteristics for high intensities of TL light. The comparison was performed using the Harshaw 3500, Risø DA-20 and RA’94 TLD readers. The instruments were tested for the readouts of highly irradiated LiF:Mg,Cu,P (MCP) TL detectors, which require readout up to 550 °C, in case of doses exceeding 1 kGy. It was found that the Harshaw 3500 can be used, without any additional light attenuation, for the measurements of MCP detectors exposed to doses up to about 5 Gy. For the other two readers the upper dose limit is about 10 times lower. It was also found that the Harshaw 3500 shows the best thermal stability considering the peak maximum position. For the ultra-high doses the differences in the spectral characteristics of the applied optical filters and photomultipliers, in conjunction with an evolution of the MCP TL emission spectrum with increasing dose, significantly influence the shape of TL glow curves measured with the DA-20 reader. The detailed characteristic of the compared TLD readers at high-dose high-temperature range is discussed.

TL emission spectra measurements using a spectrometer coupled to the Risoe TL/OSL reader

A high sensitivity spectrometer (Ocean Optics QE65 Pro) was coupled to the Risoe TL/OSL reader to measure TL emission spectra of four different dosimeters. This spectrometer is based on a Hamamatsu FFT-CCD detector with a 2-D arrangement of pixels (1044×64), which detects luminescence in a range of 200–950 nm. An optical fiber was used to guide the signal from the sample to the spectrometer. TL spectra from LiF, CaSO 4 :Dy, BeO and Al 2 O 3 :C detectors were obtained and they are presented in this work. The proposed detection system showed good response; spectra shape, in accordance with the literature, were obtained, validating the system. • A spectrometer based on a CCD detector was coupled to a TL/OSL reader via optical fiber. • TL emission spectra of well-known TL materials were measured. • The measured spectra showed the expected shapes; thus the system proved a good performance. • The set-up is very easy to use and it shows good potential to study new materials.

Synthesis and study on the luminescence properties of cadmium borate phosphors

Cadmium borate compound prepared through wet chemical reaction from the starting chemicals followed by high temperature solid state synthesis below the melting point to get the final TL phosphor powder. Phase purity and bond details of cadmium borate crystals are characterized using X-ray diffraction technique and infrared spectroscopy. Feasibility of these materials for radiation dosimetry applications was studied after gamma and neutron irradiation. Gamma irradiation of undoped phosphors show a single peak around 185°C whereas doping with gadolinium and silver, new more intense peak observed at 290°C. Irradiation to thermal neutrons revealed single peak around 170°C for all the phosphors. TL emission spectra and photoluminescence (PL) studies were also carried out on the phosphors. These borate materials are found to be highly sensitive to neutrons and hence can be used for neutron detection. Neutron sensitivity of the material is about ten times that of TLD-600.

Thermoluminescence dosimetric characteristics of thulium doped ZnB2O4 phosphor

Polycrystalline powder samples of rare earth doped Zinc borates were synthesized by high temperature solid state diffusion technique. Dosimetric characteristics of the phosphor like thermoluminescence glow curve, TL emission spectra, dose–response, fading studies, reproducibility and reusability studies were carried out on the synthesized phosphors. Among the different rare earth doped phosphors, thulium doped zinc borate was found to have a higher sensitivity. Hence detailed dosimetric characteristics of this phosphor were carried out. It is observed that the dose–response is linear from 10mGy to 103Gy in this phosphor. EPR measurements were carried out on unirradiated, gamma irradiated and annealed phosphors to identify the defect centers responsible for thermoluminescence. A TL model is proposed based on the EPR studies in these materials. Kinetic parameters were evaluated for the dosimetric peaks using various methods. The experimental results show that this phosphor can have potential applications in radiation dosimetry applications.

Measurements of high-temperature emission spectra of highly irradiated LiF:Mg,Cu,P (MCP-N) TL detectors

Abstract High-sensitive thermoluminescent detectors LiF:Mg,Cu,P have been investigated after exposures with γ-rays doses up to hundreds of kGy. Both emission spectra and TL glow curves have been measured up to temperature of 550 °C. TL emission spectra integrated over a temperature range of 47–470 °C were analyzed. Two emission regions, main (220–450 nm) and long wavelength (450–800 nm), were distinguished. No significant changes, with increasing dose, were observed in the main emission. The long wavelength emission was visible at the doses of 4 kGy and higher, indicating that such an amount of energy, deposited in the detector volume, makes additional recombination centers active. At the “B” peak temperature range (above 400 °C), the wavelength of emitted light was nearly identical, as for the main glow peak (∼220 °C) at lower doses. It tends to suggest that high-dose high-temperature emission of MCP-N occurs along the same recombination path as the emission below the saturation level. Gaussian deconvolution in the energy domain was also performed for the measured spectra. The results of deconvolution remain in a general agreement with previous measurements.

Thermoluminescence and Mechanoluminescence of Eu Doped Y2O3 Nanophosphors

Abstract Thermoluminescence and Mechanoluminescence phenomenon of Y2O3: Eu nanophosphor prepared by combustion method has reported.XRD; Optical absorption spectra have also studied. TL emission spectra show intense peak around 600 nm.