Thermoluminescence Spectra Research Articles

Synthesis and luminescent properties of novel BaGd2O4:Eu3+ scintillating phosphor

BaGd2-x O4:xEu(3+) and Ba1-y Gd1.79-2y Eu0.21 Na3y O4 phosphors were synthesized at 1300°C in air by conventional solid-state reaction method. Phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd2-x O4 :xEu(3+) and Ba1-y Gd1.79-2y Eu0.21 Na3y O4 phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu(3+) emission could only be enhanced by 1.3 times with incorporation of Na(+) into the BaGd2 O4 host. Enhanced luminescence was attributed to the flux effect of Na(+) ions. However, when BaGd2 O4:Eu(3+) phosphors were codoped with Na(+) ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu(3+) ions.

Photoluminescence of Turkish purple jade (turkiyenite)

The purple-colored unique gem material is only found in the Harmancık (Bursa) region of the western Anatolia (Turkey). Therefore, it is specially called “Turkish purple jade or turkiyenite” on the worldwide gem market. Even though its jadeite implication is the principal constituent, the material cannot be considered as a single jadeite mineral since other implications are quartz, orthoclase, epidote, chloritoid and phlogopite minerals.Even if the analytical methods are used to characterize and identify the Turkish purple jade samples in detail, the luminescence spectra, especially photoluminescence features regarding to composite mineral implications of the material are important because of the existence the numerous characteristic broad and intensive luminescence bands in the samples. We can state that the UV-irradiation luminescence centers as photoluminescence (PL) are due to the overall signals in the Turkish purple jade samples. Accordingly, the distinctive photoluminescence peaks at 743, 717, 698, 484, 465 and 442nm in PL-2D (counter diagram and sections) and PL-3D (sequence spectra) ranging between 300 and 900nm of wavelengths, and between 220 and 340K of temperatures are observed.Finally, photoluminescence features of the heterogeneous-structured material cannot be simply attributed to any chemical impurities, since the jade mass has numerous heterogeneous mineral constituents instead of a single jadeite mineral. Six different mineral implications and chemical impurities in the material composition display complex and individual all kind of luminescence features. Therefore, photoluminescence as well as radioluminescence, cathodoluminescence and thermoluminescence spectra provide positive identification regarding to the provenance (geographic origin) of the original Turkish purple jade (turkiyenite).

Luminescence and defect studies of YAlO3:Dy3+, Sm3+ single crystals exposed to 100 MeV Si7+ ion beam

Ionoluminescence (IL) and photoluminescence (PL) spectra for different rare earth ions (Sm3+ and Dy3+) activated YAlO3 single crystals have been induced with 100MeV Si7+ ions with fluence of 7.81×1012ionscm−2. Prominent IL and PL emission peaks in the range 550–725nm in Sm3+ and 482–574nm in Dy3+ were recorded. Variation of IL intensity in Dy3+ doped YAlO3 single crystals was studied in the fluence range 7.81×1012–11.71×1012ionscm−2. IL intensity is found to be high in lower ion fluences and it decreases with increase in ion fluence due to thermal quenching as a result of an increase in the sample temperature caused by ion beam irradiation. Thermoluminescence (TL) spectra were recorded for fluence of 5.2×1012ionscm−2 on pure and doped crystals at a warming rate of 5°Cs−1 at room temperature. Pure crystals show two glow peaks at 232 (Tg1) and 328°C (Tg2). However, in Sm3+ doped crystals three glow peaks at 278 (Tg1), 332 (Tg2) and 384°C (Tg3) and two glow peaks at 278 (Tg1) and 331°C (Tg2) in Dy3+ was recorded. The kinetic parameters (E, b s) were estimated using glow peak shape method. The decay of IL intensity was explained by excitation spike model.

Thermal- and photo-induced transformations of luminescence centers in αd-Al2O3 anion-defective crystals

The thermal- and photo-induced transformations of luminescence centers in anion-defective crystals of α-Al2O3 have been investigated. It has been found that the exposure of crystals to ultraviolet light at temperatures in the range 50–900°C leads to substantial changes in their thermoluminescence and radioluminescence spectra. According to the optical absorption and photoluminescence data, the detected F-type centers have been identified and the temperature ranges of the F → F+ → F2 transformations and their possible mechanisms have been determined. The special attention has been drawn to the detailed similarity in the formation of complex F2-type centers in the initially perfect α-Al2O3 crystals irradiated with fast neutrons and in the studied anion-defective crystals.

Thermoluminescence in heavily F-doped of SnO2 nanocrystals

Without external irradiation, the heavily fluorine doped SnO2 nanocrystals show a broad glow curve at 454K in the thermoluminescence spectrum. On irradiation with UV light, the glow curve of SnO2:F resolves in to two, one centred at 440K and the other at 520K. The glow curves, under different heating rates, before and after irradiation with UV light are analyzed by the Glow Curve Deconvolution procedure and peak shape methods. A major trap with activation energy of 1eV coupled with high frequency factor of order of 1010s−1 suggests it to be a potential direct contact temperature sensor.

Thermoluminescence kinetics of oxygen-related centers in AlN single crystals

Excitation and emission spectra of thermoluminescence (TL) in bulk aluminum nitride single crystals irradiated by UV have been studied. TL has been found to be most effectively excited by the 5.04eV photons. The 3.44eV band caused by recombination processes with oxygen–vacancy (VAl−ON)-centers dominates in the TL spectrum. Besides, the 2.91 and 2.0eV emissions have been also observed. The TL mechanisms have been quantitatively analyzed in terms of formal kinetics of general order. On the basis of the obtained values and from their comparison with literature data it has been concluded that the main traps of charge carriers, responsible for the TL peak at 470К, are formed by the VN vacancy. To interpret the observed regularities, the model of TL has been proposed, which satisfactorily agrees with independent data for thermally and optically stimulated processes in aluminum nitride.

Synthesis and characterisation of BaSo4:Eu thermoluminescence phosphor

Polycrystalline powder samples of BaSO(4) doped with Eu(2+) were prepared by solid-state reaction in different reducing atmospheres. Photoluminescence (PL), thermoluminescence (TL), TL kinetic and dosimetric studies have been carried out in this phosphor. The TL glow curve of BaSO(4):Eu(2+) showed only a single peak at 513 K unlike other phosphors and the TL intensity is about three to four times higher than that of CaSO(4):Dy, which is currently used as the radiation dosemeter for personnel monitoring in India. The TL dose response of the phosphor was found to be linear up to the dose range of 10(3) Gy beyond which saturation sets in. PL and TL spectra showed the characteristic emission of Eu(2+) ion. The TL parameters such as trap depth (E) or the energy required to release the electron or hole from the trap, frequency factor (s) and the order of kinetics (b) are determined by different methods such as isothermal decay, initial rise and variable heating rate.

Synthesis of a New Red Long Persistent Phosphor Sr2ZnSi2O7: Eu3+, Lu3+ via Sol–Gel Method and Investigation of its Luminescence

A novel red long persistent phosphor of Sr2ZnSi2O7: Eu3+, Lu3+ was successfully synthesized with sol–gel method. Its properties were systematically characterized by X-ray diffraction(XRD), luminescence, afterglow decay curves and thermoluminescence (TL) spectra. The red phosphor showed one emission peak at 616.9nm, which is attributed to the typical 5D0–7F2 transition of Eu3+ ions as luminescent centers in Sr2ZnSi2O7 host. Lu3+ as a sensitized ion played an important role in enhancing the long afterglow performance of Sr2ZnSi2O7: Eu3+, Lu3+. Under UV light irradiation, this phosphor showed obvious red long-lasting phosphorescence that can be clearly seen with naked eyes in a dark room for over 20s after the irradiation source has been removed. Thermoluminescence (TL) measurement showed that Lu3+ co-dopan can reduce the trap depth of the title phosphor to obtain suitable ones.

Development of new elasticoluminescent material SrMg 2(PO 4) 2:Eu

We have succeeded in developing a new elasticoluminescent (elastico-L) material SrMg 2(PO 4) 2:Eu (SMPE), which emits purple light clearly observable with the naked eye. SMPE can be synthesized at a firing temperature, which is several hundred degrees Kelvin lower than that for other materials of this group. Based on a comparison between elastico-L emission spectrum and photoluminescence spectrum, the emission was identified to be due to electron transition from an excited state 4 f 65 d 1 to the ground state 4 f 7 in Eu 2+ ions. While the emission gradually decayed as stress was applied repeatedly, it recovered completely upon irradiation with UV light (365 nm). This behavior, characteristic to elastico-L materials of the defect-controlled type, suggests that deep charge traps are involved in the emission process. In this paper, the elastico-L mechanism in SMPE is discussed in detail with reference to its thermoluminescence and electroluminescence spectra.

Sol–gel synthesis of long-lasting phosphors CdSiO3: Mn2+, RE3+ (RE = Tb, Eu, Nd) and luminescence mechanism research

Mn2+ and RE3+ (RE=Tb, Eu, Nd) co-doped CdSiO3 orange phosphors were prepared at 1050°C by a sol–gel method. The phase and crystallinity of the synthesized materials were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The luminescence characteristics were analyzed using photoluminescence (PL) spectra, afterglow decay curves, long-lasting phosphorescence spectra, and thermoluminescence (TL) spectra. Due to the difference in co-doped rare earth ionic radii, it varied greatly in trap density and trap depth caused by the different defects deriving from RE3+ ions co-doping into the CdSiO3: Mn2+ host. The afterglow intensity and time for these samples increased as follows: CdSiO3: Mn2+0.2%, Nd3+0.8%<CdSiO3: Mn2+0.4%, Tb3+0.8%<CdSiO3: Mn2+0.4%, Eu3+0.3%. CdSiO3: Mn2+0.4%, Eu3+0.3% had the best afterglow properties, which could be due to the proper traps formed by Eu3+ ions co-doping into the host. The role of RE3+ co-doped into the CdSiO3: Mn2+ matrix and the possible long-lasting phosphorescence process was also discussed in this paper.

Enhanced luminescence of Ca 3B 2O 6:Dy 3+ phosphors by Na +-codoping for LED applications

The Ca 2.95− y Dy 0.05B 2O 6: yNa + (0≤ y≤0.20) phosphors were synthesized at 1100 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE), photoluminescence (PL) spectra and thermoluminescence (TL) spectra. The PLE spectra show the excitation peaks from 300 to 400 nm due to the 4f–4f transitions of Dy 3+. This mercury-free excitation is useful for solid-state lighting and light-emitting diodes (LEDs). The emission of Dy 3+ ions on 350 nm excitation was observed at 480 nm (blue) due to the 4F 9/2→ 6H 15/2 transitions, 575 nm (yellow) due to 4F 9/2→ 6H 13/2 transitions and 660 nm (red) due to weak 4F 9/2→ 6H 11/2 emissions. The PL results from the investigated Ca 2.95− y Dy 0.05B 2O 6: yNa + phosphors show that Dy 3+ emissions increase with the increase of the Na + codoping ions. The integral intensity of yellow to blue ( Y/ B) can be tuned by controlling Na + content. By the simulation of white light, the optimal CIE value (0.328, 0.334) can be achieved when the content of Na +-codoping ions is y=0.2. The results imply that the Ca 2.95− y Dy 0.05B 2O 6: yNa + phosphors could be potentially used as white LEDs.

Luminescence characterization of gamma-ray-irradiated rare-earth doped BaSO4 and MgSO4 phosphors

Abstract Photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) of rare-earths (RE) doped BaSO4 and MgSO4 phosphors were studied. Undoped and doped phosphors containing different concentrations of dopant were synthesized by solid-state reaction method. X-ray diffraction (XRD) pattern of the samples matched well with their standard data of Joint Committee on Powder Diffraction’s (JCPD) file. In the PL spectrum of Dy doped samples, peaks around 470 and 580 nm were observed due to transition of Dy3+ ion. Eu doped BaSO4 showed PL peak at 380 nm due to transition of Eu2+ ion, however, in the PL spectrum of MgSO4:Eu phosphors, transition of Eu3+ was also observed along with transition of Eu2+ ion. Dy doped γ-ray-irradiated BaSO4 and MgSO4 phosphors showed at least two distinct peaks in their TL glow curves. The first peak occurred in range 120–150 °C and the second peak was observed in the range 220–230 °C. The TL glow curve of γ-ray-irradiated BaSO4:Eu contained a distinct peak at 170 °C. Two distinct peaks, one at 110 °C and another at 220 °C were observed in the TL glow curve of γ-ray-irradiated MgSO4:Eu phosphors. TL spectra showed that RE ions act as luminescence centre in BaSO4 and MgSO4 system. When the ML was excited impulsively by dropping a load on to the γ-ray-irradiated samples, only one sharp peak was observed in the ML intensity versus time curve of Dy doped samples, however, two peaks were observed in the ML intensity versus time curve of Eu doped BaSO4 and MgSO4 phosphors. The ML spectra of samples showed the characteristic emission of rare-earth impurities. Experimental results suggest that although almost similar states are responsible for PL, TL and ML, the luminescence efficiency of the phosphors depends on the mode of excitation.

The persistent energy transfer of Eu 2+ and Mn 2+ and the thermoluminescence properties of long-lasting phosphor Sr 3MgSi 2O 8:Eu 2+, Mn 2+, Dy 3+

Eu 2+, Mn 2+ and Dy 3+ co-doped long-lasting phosphors Sr 3MgSi 2O 8 were prepared by a solid-state reaction under a reductive atmosphere. Fluorescence spectra demonstrated that the weak red emission resulting from the forbidden transition of Mn 2+ could be enhanced by the energy transfer from Eu 2+ to Mn 2+. The energy transfer between Eu 2+ and Mn 2+ was systematically investigated. The phosphorescence spectra revealed that Eu 2+ could persistently transfer its energy to Mn 2+ after removing the excitation source. The duration of Mn 2+ can prolong to more than 2 h. The thermoluminescence spectra were used to characterize the ability of the trap to trapping the carriers. By the analysis of the ionization potentials, the roles of Mn 2+ and Dy 3+ in the afterglow process were discussed. A possible afterglow mechanism was presented and discussed.

Recombination luminescence of poly(arylene phthalide) films induced by visible light

Long-term afterglow emission (AG) of poly(arylene phthalide) films (PAP) irradiated with visible light has been discovered. Recombination nature of the AG was experimentally proven as in the case of UV irradiation. Features of the observed AG spectra were analyzed in comparison with the photo-, electro-, and thermoluminescence spectra of the PAP films in relation to the commonness of the AG generation mechanism, which is associated with the involvement of the two-photon reactions and triplet states in the photoprocesses in PAP.

Radioluminescence and thermoluminescence of albite at low temperature

Abstract Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25–280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi 3 O 8 and the plagioclases (NaAlSi 3 O 8 –CaAl 2 Si 2 O 8 ) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na + , Mn 2+ or Fe 3+ ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials.

Preparation and properties of CdSiO3: Mn2+, Tb3+ phosphor

CdSiO3: Mn2+, Tb3+ long-lasting phosphor was prepared by the conventional high temperature solid-state method. Effects of the content of Mn2+ and Tb3+ on the luminescent properties of phosphor CdSiO3: Mn2+, Tb3+ were investigated by means of photoluminescence (PL) spectra, the afterglow intensity decay curves and the thermoluminescence (TL) spectra. It was found that when the Mn2+ and Tb3+ dopant-concentrations were 0.4mol% and 0.8mol% of Cd2+ ions in CdSiO3, respectively, the luminescence of phosphor prepared had better luminescent property and longer afterglow time. Role of Tb3+ co-doped into CdSiO3: Mn2+ matrix was discussed in this paper.

A new long-lasting phosphor Zr 4+ and Eu 3+ co-doped SrMg 2(PO 4) 2

Zr 4+- and Eu 3+-codoped SrMg 2(PO 4) 2 phosphors were prepared by conventional solid-state reaction. Under the excitation of ultraviolet light, the emission spectra of Sr 0.95Eu 0.05Mg 2−2 x Zr 2 x P 2O 8 ( x = 0.0005–0.07) are composed of a broad emission band peaking at 500 nm from Zr 4+-emission and the characteristic emission lines from the 5D 0 → 7F J ( J = 0, 1, 2, 3 and 4) transitions of Eu 3+ ions. These phosphors show the long-lasting phosphorescence. The emission color varies from red to white with increasing Zr 4+-content. The white-light emission is realized in single-phase phosphor of Sr 0.95Eu 0.05Mg 2−2 x Zr 2 x P 2O 8 ( x = 0.07) by combining the Zr 4+- and Eu 3+-emission. The duration of the persistent luminescence of Sr 0.95Eu 0.05Mg 2−2 x Zr 2 x P 2O 8 ( x = 0.07) reaches nearly 1.5 h. The time at which the long-lasting phosphorescence intensity is 50% of its original value ( T 0.5) is 410 s. The afterglow decay curves and the thermoluminescence spectra were measured to discuss this long-lasting phosphorescence phenomenon. The co-doped Zr 4+ ions act as both the luminescence centers and trap-creating ions.

Sol-gel preparation and phosphorescence property of Mn2+-doped zinc borosilicate glass thin films

Mn2+-doped zinc borosilicate (ZBSM) glass thin films were first synthesized by sol-gel method. In the experiment, a thin gel film was deposited onto quartz glass substrates by dip-coating method and then heat-treated to form a Mn2+-doped zinc borosilicate glass thin film. Long lasting phosphorescence (LLP) and photo-stimulated long lasting phosphorescence (PSLLP) were found in the film sample. According to fluorescence spectra, LLP emission spectra, and PSLLP emission spectra, both LLP and PSLLP emissions are attributed to the energy level transition of 4Eg→4A1g from Mn2+. Both the phosphorescence intensity decay curves contain a fast decay component and another slow decay one. The thermoluminescence (TL) spectra show that the sample has two kinds of traps at least and their energy level values are about 0.8 eV and 1.02 eV, which could be estimated by the Randall and Willcins formula. The infrared absorption spectra (IR) consist of characteristic vibration bands of Si-O-Si, Si-O-Zn, B-O in [BO3], B-O group, and Zn-O in [ZnO4]. Moreover, image storage and logical operation of the ZBSM film were carried out successfully through an experiment analogues of optical storage.

Pure and Sn-, Ga- and Mn-doped ZnO gas sensors working at different temperatures for formaldehyde, humidity, NH3, toluene and CO

ZnO and Sn-, Ga- and Mn-doped ZnO nanoparticles were prepared by a coprecipitation method, and characterized by scanning electron microscopy (SEM), energy dispersive spectra (EDS), X-ray diffraction (XRD) and Raman spectra. The gas sensing properties were studied using formaldehyde, relative humidity, NH3, toluene and CO as the probes. The results show that all particles have wurtzite ZnO phase, though Sn–ZnO has a relatively smaller particle (and crystallite) size than the other three samples. Gas sensing property tests reveal that the temperature where the gas sensing maximum is gained (TM) is changed by different dopants: Sn–ZnO and Mn–ZnO have relatively lower TM (∼100°C lower) compared with that of pure ZnO, while Ga–ZnO has the same TM as pure ZnO except in CO sensing. Thermoluminescence (TL) spectra were used to investigate the mechanism of TM change. The peak positions of Ga–ZnO and ZnO are the same at 300–350°C, while that of Sn–ZnO shifts to 250–300°C, which might contribute to the same TM of Ga–ZnO and pure ZnO and relatively lower TM of Sn–ZnO. In the case of Mn–ZnO, the luminescence emission is evidently limited by its black color.

Reddish orange long afterglow phosphor Ca 2SnO 4:Sm 3+prepared by sol–gel method

A reddish orange light emissive long afterglow phosphor, Ca 2SnO 4:Sm 3+ was prepared by sol–gel method at lower temperature. The synthesized phosphors were characterized by X-ray diffraction, scanning electron micrograph images, photoluminescence spectra, afterglow decay curves and thermoluminescence spectra. Three emission peaks locate at 565 nm, 609 nm and 655 nm corresponding to CIE chromaticity coordinates of x = 0.53 and y = 0.47, which indicates the reddish orange light emitting. The fluorescent intensity and the afterglow characteristic depends on the concentration of Sm 3+ and the optimized concentration is 1.5 mol%. The afterglow decay curves are well fitted with triple-exponential decay models. The thermoluminescence glow curves show that the Sm 3+ induces suitable trap depth and result in the long afterglow phenomenon, and the corresponding increase or decrease in afterglow is associated with trap concentration, nearly no change in trap depth. The 1.5 mol% Sm 3+-doped Ca 2SnO 4 sample has the biggest trap concentration and exhibit the best afterglow characteristic, its’ afterglow time is about 1 h. The phosphorescence mechanism of this long afterglow phosphor was discussed.