Thermoluminescence and optically stimulated luminescence characteristics of Al2O3 doped with Tb

In the present work policrystals of α − Al₂O₃ doped with terbium were synthesized using the solvent evaporation method. The samples were prepared using Al(NO₃)₃·9H₂O and Tb(NO₃)₃·5H₂O reagents, with Tb concentrations between 1 and 5 mol% and thermally treated at high temperature above ∼1400 °C. X-ray diffraction measurements showed the α-phase formation of samples. TL glow curve presented an intense peak at ∼190 °C and two other with low intensity at 290 and 350 °C after gamma irradiation. The best doping concentration which presented high luminescence was the sample doped with 3 mol% of Tb. TL spectra and fluorescence measurements showed similar luminescence spectra with lines attribute to Tb³⁺ ions. A linear behavior to gamma dose between 1 and 20 Gy was observed in TL, using 190 °C peak as well as in OSL signal, this last carried out using 532 nm wavelength stimulation.     

Thermoluminescence and photoluminescence studies on gamma irradiated CsI: Pb2+ crystals

Pure and Pb²⁺-doped CsI crystals have been grown by the Bridgemann technique. Optical absorption, thermoluminescence (TL) and photoluminescence (PL) measurements have been performed. In undoped and Pb²⁺-doped cesium iodide crystals, F-centers and V-centers have been produced at 770 nm and 350 nm, respectively. In Pb²⁺-doped crystals, additional centers at 373 nm, 290 nm and 258 nm bands have been produced. In undoped samples, only two glow peaks at 343 K and 373 K have been produced, and in Pb²⁺-doped samples additional glow peaks at 383 K and 423 K have been produced. For all the samples, TL emission, PL and excitation measurements have been performed.     

Thermoluminescence characteristics of rare-earth-doped LiCaBO3 phosphor

LiCaBO₃ was synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy³⁺, Tb³⁺, Tm³⁺ and Ce³⁺, on thermoluminescence (TL) of LiCaBO₃ phosphor was discussed. We studied the TL properties and some dosimetric characteristics of Ce³⁺-activated LiCaBO₃ phosphor in detail. The effect of the concentration of Ce³⁺ on TL was investigated, the result of which showed that the optimum Ce³⁺ concentration was 1 mol%. The TL kinetic parameters of LiCaBO₃:0.01Ce³⁺ were studied by computer glow curve deconvolution (CGCD) method. The three-dimensional (3D) TL emission spectra were also studied, peaking at 431 and 474 nm due to the characteristic transition of Ce³⁺. We also studied the linearity, annealing condition, reproducibility, fading and different heating rate of the LiCaBO₃:0.01Ce³⁺ phosphor.     

Lu2SiO5∶Ce荧光粉的热释光特性研究

采用溶胶-凝胶(Sol-Gel)技术,分别在空气中和石墨提供的弱还原气氛下制备出Lu2SiO5∶Ce0.006荧光粉。通过分析样品的结构,光致激发、发射谱和热释光谱等特性,发现弱还原气氛下制备的样品不仅光致发光强度比空气中的强,而且热释光曲线中598K处的高温热释光峰也得到了抑制。进一步考察空气中制备的Lu2SiO5∶Ce0.006,Kx(x=0.01～0.08)荧光粉,结果表明就光致发光和热释光特性而言,K+共掺杂具有与还原气氛类似的作用。综合以上两方面分析结果,可认为598K处热释光峰是由与Ce4+相关的缺陷引起的,并对K+共掺杂LSO∶Ce发光增强的原因给出了合理解释。     

Synthesis and characterization of BaAl2O4:Eu co-doped with different rare earth ions

Combustion method was used in this study to prepare BaAl₂O₄:Eu²⁺ phosphors co-doped with different trivalent rare-earths (Re³⁺=Dy³⁺, Nd³⁺, Gd³⁺, Sm³⁺, Ce³⁺, Er³⁺, Pr³⁺ and Tb³⁺) ions at an initiating temperature of 600 °C. The phosphors were annealed at 1000 °C for 3 h. As confirmed from the X-ray diffraction (XRD) data, both as prepared and post annealed samples crystallized in the well known hexagonal structure of BaAl₂O₄. All samples exhibited bluish-green emission associated with the 4f⁶5d¹→4f⁷ transitions of Eu²⁺ at ∼500 nm. Although the highest intensity was observed from Er³⁺ co-doping, the longest afterglow (due to trapping and detrapping of charge carriers) was observed from Nd³⁺ followed by Dy³⁺ co-doping. The traps responsible for the long afterglow were studied using thermoluminescence (TL) spectroscopy.     

Thermoluminescence, structural and magnetic properties of a Li2O-B2O3-Al2O3 glass system doped with LiF and TiO2

A Li₂O-B₂O₃-Al₂O₃ glass system, un-doped and doped with LiF, and/or TiO₂ was synthesized by the fusion method and its physical properties were investigated by thermoluminescence (TL), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), atomic force microscopy (AFM) and differential thermal analysis (DTA). The samples were subjected to γ-rays from a colbalt-60 (⁶⁰Co) source. These techniques provided evidence of LiF and LiF doped with Ti crystal formation in the glass system. A TL glow peak at about 433 K was sensitive to ⁶⁰Co γ-rays and showed good linearity with doses and consequently could be used to quantify radiation doses.     

Thermoluminescence of B2O3-Li2O glass system doped with MgO

Lithium borate (LiB) glasses in the system (100−x)B₂O₃-xLi₂O with x=20, 30, 40, 50, 60 and 70 mol% were prepared. The glasses were doped with different concentrations of the order of 10⁻¹, 10⁻², 10⁻³, 10⁻⁴ and 10⁻⁵ of MgO and their thermoluminescent (TL) response was investigated. The irradiations were performed using γ rays from a ⁶⁰Co source in the dose range from 0.1 to 25 kGy. The material displayed good sensitivity for γ-rays and intensity of TL signals is dependent on γ-ray dose and Li₂O content. For each dose level and investigated temperature range (50-350 °C), exactly single isolated glow peak appears in the temperature range of 165-205 °C depending on both Li₂O concentrations and time of exposure. The shape of the glow peak has altered significantly with increase in the gamma ray dose or Li₂O concentrations. The glass composition with x=50 mol% doped with 10⁻³ mol% of MgO presented the best TL response. The results of the present study indicated that the recorded single and isolated high temperature peak is a good candidate for TL dosimetric investigations. This indicates that 50 B₂O₃-50Li₂O-doped with 10⁻³ mol% of MgO is possibly used as materials for radiation dosimetry in the dose range of 0.1-20 kGy.     

Luminescence characteristics of Dy3+ activated Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphor

In this paper, we have reported a new Na ₂Sr ₂Mg (BO ₃)₂F ₂:Dy ³⁺ thermoluminescence (TL) phosphor prepared via the wet chemical method. Prepared phosphor was characterized by X-ray powder diffraction, photoluminescence (PL), TL and scanning electronmicroscopy techniques. The scanning electronmicroscopic image of Na ₂Sr ₂Mg (BO ₃)₂F ₂:Dy ³⁺ phosphor confirms the micron size of particles. Under the PL study, the characteristic emission spectrum of Dy ³⁺ corresponding to ⁴F _9/2→⁶H _15/2 (481 nm) and ⁴F _9/2→⁶H _13/2 (576 nm) transitions was observed. The TL property of the as prepared phosphor was also found to be good. TL intensity of Na ₂Sr₂Mg(BO ₃)F ₂:Dy ³⁺ phosphors at 0.99 kGy exposure of γ-irradiations was compared with standard CaSO ₄:Dy phosphor. It was seen that TL intensity of Na ₂Sr ₂Mg (BO ₃)₂F ₂: Dy ³⁺ phosphors is 1.1 times less compared with the standard CaSO ₄:Dy TL dosimeter phosphor. The kinetic parameters are also discussed in detail. The values of activation energy E (eV) and frequency factor S (s ^?1) were found to be 0.57 eV and 1.25×10⁶ s^?1, respectively.     

Crystal structure and photoluminescence properties of Eu-activated Ba2LiB5O10 phosphors

A novel orange-yellow-emitting Ba₂LiB₅O₁₀:Eu²⁺ phosphor has been synthesized by traditional high temperature solid state reaction. A monoclinic crystal structure of Barium lithiumborates Ba₂LiB₅O₁₀ was verified by the investigation of X-ray diffraction (XRD). The compound crystallizes in the space group of P121/m1(11) (Z = 2) with the unit cell parameters a = 4.414(1) Å, b = 14.576(2) Å, c = 6.697(2) Å and β = 104.26(2)°. Barium and lithium atoms are located in distorted octahedral and tetrahedral oxygen coordinations, respectively. Upon around 365 nm excitation, the Eu²⁺-activated Ba₂LiB₅O₁₀ phosphors exhibit a single broad emission band with the maximum at about 587 nm, due to the 4f⁶5d → 4f⁷(8S_7/2) transition of Eu²⁺. This work investigates the relationship between luminescence properties and structural characterization of the Ba₂LiB₅O₁₀: Eu²⁺. This newly developed phosphor shows high potential as a phosphor conversion for white LED applications.     

Thermoluminescent properties of a Li2O-B2O3-Al2O3 glass system doped with CaF2 and Mn

A Li₂O-B₂O₃-Al₂O₃ glass system doped with CaF₂ and Mn was synthesized by fusion and its physical properties were investigated using thermoluminescence (TL) and differential thermal analysis (DTA) techniques. The TL glow curve peaks, resulting from this analysis, are characteristic of metastable levels intrinsic to CaF₂ crystals that have undergone γ-ray irradiation from a colbalt-60 (⁶⁰Co) source. This provides evidence of CaF₂ crystal formation in the glass system. Furthermore, the TL glow peak at about 480 K was stable at room temperature, sensitive to ⁶⁰Co γ-rays and showed good linearity with doses ranging from 3 Gy to approximately 100 Gy, and consequently could be used to quantify radiation doses. High quality synthesis of these crystals permits control of their thermoluminescent properties.     

Effects of Tb doping on the photoluminescence of Y2O3:Tb nanophosphors

The effects of Tb doping on the photoluminescence (PL) of Y₂O₃:Tb nanophosphors have been investigated. Nanophosphors were prepared by the glycine-nitrate solution combustion technique using yttria and terbia powders as precursors. PL excitation spectra at room temperature consist of two overlapping bands centered at 277 and 304 nm, whereas emission spectra comprise several groups of lines corresponding to the ⁵D₄→⁷F_J (J=1-6) 4f electronic transitions of the Tb⁺³ ions. A direct comparison of nanophosphor and bulk concentration-quenching curves was obtained by annealing the nanophosphor powder and converting it to bulk material without altering the Tb concentration. The peak in the nanophosphor concentration-quenching curve occurs at a concentration ∼3 times higher than that of the bulk.     

Thermoluminescence and photoluminescence of LiNaSO4:Eu irradiated with 24 and 48 MeV Li ion beam

Thermoluminescence (TL) of LiNaSO₄:Eu phosphor, irradiated with 24 and 48 MeV ⁷Li ions at different fluences in the range 5×10⁹-1×10¹² ion/cm², has been studied. The samples from the same batch were also exposed to γ-rays from a Cs¹³⁷ source for comparative studies. The TL glow curves of the materials, irradiated with ⁷Li ions, have similar structures to that of γ-irradiated sample. They have a simple structure with a prominent peak at 412 K along with small one at around 481 K. The intensity ratios of 412-481 K peaks have been observed to increase with fluence increasing, while that of γ-irradiated sample shows a reverse trend. This could be attributed to the changes in the recombination center populations due to ⁷Li ions, that have been implanted inside the matrix of LiNaSO₄:Eu, during irradiation and might also act as a source for new trapping and luminescent centers. The implantation has been confirmed by TRIM calculations. The penetration depths (where the ion comes to rest) are found to be 145 and 463 μm corresponding to 24 and 48 MeV ion beam energies, respectively, which are less than the thickness of the sample chips (∼800 μm). The efficiencies of LiNaSO₄:Eu to 24 and 48 MeV ⁷Li ions measured relative to γ-rays of Cs¹³⁷ are found to be 0.007 and 0.024, respectively. Theoretical analysis of the glow curves of the samples irradiated by ⁷Li ions and γ-rays were done by glow curve deconvolution method to determine trapping parameters of various peaks. The experimentally observed linearity/sublinearity has been discussed in the frame of track interaction model. Photoluminescence studies in the ⁷Li ions irradiated and un-irradiated samples show that europium ions have incorporated in the host in their divalent (emission at 440 nm) as well as trivalent (emissions at 594, 615 and 700 nm) forms. The intensities of the emission bands of these ions have been observed to increase with fluence increasing.     

Preliminary TL Studies of K2GdF5:Dy3+ exposed to photon and neutron radiation fields

Results of the investigation concerning thermoluminescence (TL) responses to X, gamma and neutron radiation fields for crystals of complex fluoride K₂GdF₅ undoped and doped with varying concentrations of Dy³⁺ ions are presented. Crystals doped with 5.0 at% Dy³⁺ have shown the most efficient TL response, with a linear response to doses for all the radiation fields. In the X rays range, the maximum TL response has been found to be 15 times more than the response for gamma. The fast and thermal neutron TL outputs were evaluated for K₂Gd_0.95Y_0.05F₅ and the contribution of the gamma component in the TL curve was estimated.     

The Effect of Zinc Ions on the Fluorescence Spectra of (Ln,Zn)of:Eu3+(Ln=Y,La and Gd) Powder Phosphors

This research note reports the fluorescence properties of Eu³⁺-doped in three sets of (Y-Zn, La-Zn and Gd-Zn) oxy fluoride powder phosphors. on excitation with a UV-source, these phosphors have displayed orangish-red color and for which the chromaticity coordinates ([Xbar], [Ybar] have been computed. the relative fluorescence intensity ratios (R) for the different measured emission transitions have been evaluated in order to examine the effect of substitution of zinc ions in the host matrix on the fluorescence behavior. Scanning electron microscopy studies have also been performed to investigate the average grain size of the synthesized phosphor material.     

Preparation and luminescent properties of phosphor MGd2(MoO4)4: Eu (M=Ca, Sr and Ba)

Intense red emitting phosphors MGd₂(MoO₄)₄: Eu³⁺ (M=Ca, Sr and Ba) have been synthesized by the simple sol-gel technique. The formation processes and the phase impurity of phosphors are characterized by thermogravimetry-differential thermal analysis (TG-DTA) and power X-ray diffraction (XRD). The narrower size distribution and the regular shape of the phosphor particles are also measured by Field emission scanning electronic microscopy (FE-SEM). Photo-luminescent properties of the phosphors are performed at room temperature. Their excitation spectra present strong absorption at 395 nm near-UV light and 465 nm blue light, which match well with commercial LED chips. The phosphors exhibit satisfactory and excellent red light dominated by 616 nm and their photoluminescence intensity is about 3-4 times stronger than that of phosphor YAG under the 465 nm excitation. In addition, the optimal concentrations of Eu³⁺ for phosphors MGd₂(MoO₄)₄ (M=Ca, Sr and Ba) have also been determined.     

Synthesis and cathodoluminescent properties of Y2SiO5:Tb3+ phosphors prepared from uniform precursor

The luminescent properties of phosphors are sensitive to the size of phosphor particles. The commercial Y₂SiO₅:Tb³⁺ phosphors usually show relatively larger particle size (5–10 μm) due to the irregular morphology of rare earth oxide precursor and thus degrade the luminescent properties. In this paper, we report the Y₂SiO₅:Tb³⁺ phosphors synthesized from the uniform Tb-doped Y₂O₃ precursor by a homogeneous precipitation method. Compared with the commercial phosphors, the obtained Y₂SiO₅:Tb³⁺ phosphors manifest the uniform morphology with much smaller particles distributing from 0.8 μm to 1.9 μm. Consequently, the cathodoluminescent intensity under low excitation voltage (1–5 kV) was increased, demonstrating a strong green emission with a dominant wavelength of 545 nm. Our results indicate an effective way to develop the high-quality phosphors for field emission display.     

Effect of Eu contents on the structure and properties of BaLa2ZnO5:Eu phosphors

A series of Eu³⁺ doped BaLa₂ZnO₅ was prepared by a Pechini-type sol-gel method. The effect of Eu³⁺ concentration on the structure and the luminescent properties of the samples BaLa_2−xEu_xZnO₅ were investigated by powder X-ray diffraction (XRD) and photoluminescence (PL) spectra. The sample adopts the tetragonal or orthorhombic structure as the Eu³⁺ concentration reaches below 1.2 or over 1.6, respectively. The sample is a mixture of tetragonal and orthorhombic phases as the contents of dopants lie between 1.2 and 1.6. The phosphor offers the strongest red light as content of Eu³⁺ is 0.4. In addition, the crystallization processes of the complex precursors were examined by simultaneous thermogravimetry and differential thermal analysis (TG-DTA), and also the optimal heating temperature was investigated.     

The response of thermally and optically stimulated luminescence from Al2O3:C to high-energy heavy charged particles

The thermoluminescence (TL) and optically stimulated luminescence (OSL) response of Al₂O₃ dosimeters to high-energy heavy charged particles (HCP) has been studied using the heavy ion medical accelarator at Chiba, Japan. The samples were Al₂O₃ single-crystal chips, of the type usually known as TLD-500, and Luxel^TM dosimeters (Al₂O₃:C powder in plastic) from Landauer Inc. The samples were exposed to ⁴He (150 MeV/u), ¹²C (400 MeV/u), ²⁸Si (490 MeV/u) and ⁵⁶Fe (500 MeV/u) ions, with linear energy transfer values covering the range from 2.26 to 189 keV/μm in water and doses from 1 to 100 mGy (to water). A ⁹⁰Sr/⁹⁰Y beta source, calibrated against a ⁶⁰Co secondary standard, was used for calibration purposes. For OSL, we used both continuous-wave OSL measurements (CW-OSL, using green light stimulation at 525 nm) and pulsed OSL measurements (POSL, using 532 nm stimulation from a Nd:YAG Q-switched laser). The efficiencies (η_HCP,γ) of the different HCPs at producing OSL or TL were observed to depend not only upon the linear energy transfer (LET) of the HCP, but also upon the sample type (single crystal chip or Luxel^TM) and the luminescence method used to define the signal—i.e. TL, CW-OSL initial intensity, CW-OSL total area, or POSL. Observed changes in shape of the decay curve lead to potential methods for extracting LET information of unknown radiation fields. A discussion of the results is given, including the potential use of OSL from Al₂O₃ in the areas of space radiation dosimetry and radiation oncology.     

Tb3+掺杂Y2O3纳米晶体中Tb3+离子4f5d跃迁及能量传递的研究

采用燃烧法制备了不同Tb3 掺杂浓度和不同粒径的Y2O3:Tb纳米晶体粉末样品,并通过高温退火获得了相应Tb3 掺杂浓度的体材料样品。测量了纳米和体材料样品的发射光谱、激发光谱、X射线衍射谱和荧光衰减曲线,并拍摄了不同粒径样品的透射电子显微镜(TEM)照片。研究纳米Y2O3∶Tb晶体粉末中Tb3 离子的4f5d跃迁发现,由于在近表面的低结晶度环境和颗粒内部的高结晶度环境中Tb3 离子4f5d跃迁对应的激发峰位置不同,不同粒径样品中处于这两种环境的Tb3 离子比例也不同,激发谱的谱线形状存在较大差别,还对Tb3 离子的能量传递进行了研究,发现Y2O3∶Tb晶体粉末中Tb3 的(5D3,7F6)→(5D4,7F0)能量传递类型为受纳米限域效应影响很大的电偶极电偶极相互作用;引起5D4→7F5(543nm)发光浓度猝灭的是不同Tb3 离子5D4能级之间交换相互类型的能量传递,此类型的能量传递受纳米限域效应影响较小。