A new mechanoluminescence phosphor Na3Sc2(PO4)3:Eu2+: Phase transition-assisted defect formation in a polymorphic composition

A new mechanoluminescent phosphor was developed from a sodium (Na) superionic conductor (NASICON)-structured Na₃Sc₂(PO₄)₃:Eu²⁺ phosphor that is known for its self-healing properties. The compound that crystalized assuming monoclinic C2/c symmetry was found to be blue-emitting, with no noticeable persistent luminescence. Thermoluminescence analysis showed that the phosphor had two prominent distinct thermal emission bands corresponding to the high-temperature β- and γ-phases of the composition. The mechanoluminescence properties of the material that does not have any persistent luminescence at room temperature were investigated by imparting impulsive strain. The compound on charging with 365 nm radiation was found to have significant mechanoluminescent emission originating from shallow defects present in the β-phase of composition that formed by the stress-induced phase transition process. Its emission characteristics and temporal behavior were investigated by varying the impact velocity.     

Identification of photoluminescence features of an epoxy resin based on components features and curing effects

Photoluminescence features in a commercial grade cured DGEBA-based epoxy resin have been investigated with as objective to determine which of the material compounds are responsible for cured resin emissions. The origin of the bands has been approached by considering photoluminescence of base resin and hardener taken separately, of their mixture, and in the course of curing. Most of the bands observed in the cured resin could be interpreted based on those found in the components taken separately. Fluorescence of the cured resin appears dominated by two broad bands that are characteristic of the hardener and exhibits a blue shift by up to 30 nm in the course of curing which could be used for cure monitoring purpose of the investigated system. Fluorescence of the base resin is clearly detected in the resin cured with tertiary amine as catalyser. However, it is very weak if the catalyser is not added. Two phosphorescence processes have been isolated in the cured resin, one of them being related to the base resin. Finally, a chemiluminescence spectrum has been recorded in the course of curing, which has been related to either curing-related reactions or to an oxidation process.     

两种新型热释光剂量计

报告两种可报告於年代测定实验室的热释光剂量计，它们是ＴＬＤ－ＱＦ３０１和ＴＬＤ－ＦＦ３０１。给出它们对各类辐射响应的特征，分别以实验数据图表明了各自的适用范围。     

Low temperature thermoluminescence properties of Eu and R doped CaAl2O4

The thermoluminescence (TL) of calcium aluminate persistent luminescence materials doped with Eu²⁺ and co-doped with R³⁺ ions were studied between 20 and 325 K. The basic material, CaAl₂O₄:Eu²⁺, showed three TL bands between 150 and 300 K in the glow curve. Changing the R³⁺ co-dopant to the adjacent element in the rare earth series affects significantly the thermoluminescence intensity and even the position of the glow curve maximum. The physical effect seemed to be removing the traps since the La³⁺, Y³⁺, and Lu³⁺ ions suppressed the thermoluminescence. The Pr³⁺, Ho³⁺, and Dy³⁺ co-doping enhanced mainly the low temperature traps and these materials have an intense but relatively short persistent luminescence at room temperature. The Nd³⁺ and Tm³⁺ ions enhanced the TL bands close to room temperature and are thus the most suitable co-dopants to induce intense and long persistent luminescence. The quenching of the thermoluminescence by Sm³⁺ was concluded to be due to the presence of Sm²⁺ that removes totally the traps.     

Li284O7：Cu，In的热释光晒退特性研究

制得一系列不同烧结温度的Li284O7：Cu，In样品，以X光衍射（XRD）、热释光（TL）、光释光（OSL）等手段研究样品的热释光陷阱的晒退特性。烧结温度对热释光陷阱的晒退特性影响较大，实验表明750℃烧结样品的热释光不易晒退。结合XRD和OSL的结果解释了烧结温度对晒退特性的影响。     

Cathodoluminescence mapping and thermoluminescence of Pr3+ doped in a CaTiO3/CaGa2O4 composite phosphor

In order to probe the properties of the one pot prepared composite phosphor of CaTiO₃ and CaGa₂O₄, cathodoluminescence mapping, thermoluminescence and lifetime measurements were carried out. The structural study showed both irregular and rod shaped particles, which match with CaTiO₃ and CaGa₂O₄, respectively, according the x-ray maps. The cathodoluminescence spectrum showed emission peaks from ³P₀→³H₄ and ¹D₂→³H₄ transitions, with the earlier transition completely absent in CaTiO₃:Pr emission at room temperature. The diffuse reflectance spectrum showed a shifted band of the inter-valence charge transfer from 360 nm to 388 nm, which is not observable for CaTiO₃:Pr³⁺and CaGa₂O₄:Pr³⁺. Additionally, the phosphorescence decay curve was recorded and the presence of electron trapping centers was confirmed using thermoluminescence spectroscopy.     

Effect of europium doping levels on photoluminescence and thermoluminescence of strontium yttrium oxide phosphor

The present paper deals with the effect of europium (Eu³⁺) doping concentration (0.1–2.5 mol%) on photoluminescence (PL) and thermoluminescence (TL) of strontium yttrium oxide (SrY₂O₄) phosphor. The sample was prepared by the modified solid state reaction method, which is the most suitable method for large-scale production. The prepared phosphor sample was characterized by using X-ray Diffraction (XRD), field emission gun scanning electron microscopy, fourier transform infrared spectroscopy, high resolution transmission electron microscopy, photoluminescence, thermoluminescence and commission internationale de I׳Eclairage techniques. The PL emission was observed in the range of 410–630 nm for the SrY₂O₄ phosphor doped with Eu³⁺. Excitation spectrum was found at 254 and 325 nm, sharp peaks were found around 593, 615 and 625 nm with high intensity. From the XRD data, using Scherrer׳s formula, calculated average crystallite size of Eu³⁺ doped SrY₂O₄ phosphor is around 32 nm. Thermoluminescence study was carried out for the phosphor with UV and gamma irradiation. The TL response of SrY₂O₄:Eu³⁺ phosphor for two different radiations was compared and studied in detail. The present phosphor can act as a single host for white light emission in display devices. The detailed process and possible mechanisms for PL and TL are studied and discussed. For the variable concentration of Eu³⁺ on PL studies the PL intensity increases with increasing the concentration of dopant and the concentration quenching found after 2 mol% of Eu³⁺ the optimized concentration was 2 mol%, which is suitable for the display device application. In TL glow curve the optimized concentration was 1 mol% for the UV irradiated sample and 0.2 mol% of Eu³⁺ for the gamma irradiated sample and beta irradiated sample for 10 Gy dose. The kinetic parameters were calculated by the computerized glow curve deconvolution (CGCD) technique.     

Comprehensive study on structural,thermal, morphological and luminescence (RL,PL, TL) properties of CaLa2(WO4)4: Tb3+, Dy3+ phosphors synthesized via sol-gel method

Tb³⁺/Dy³⁺ co-doped CaLa₂(WO₄)₄ (CLW: Tb³⁺/Dy³⁺) and its derivatives were synthesized by the sol-gel method. The morphology, thermal, structure and luminescent-optical properties the as-prepared light-emitting phosphors were characterized by utilizing scanning electron microscopy (SEM), differential thermal analysis (DTA)-thermogravimetric analysis (TG), X-ray diffraction (XRD) and radioluminescence (RL or X-ray luminescence) - photoluminescence (PL) –thermoluminescence (TL or TSL) - optical absorption spectrometry. The Tb³⁺ and Dy³⁺ ions were singly or doubly doped and the results were examined in detail. Moreover, for these phosphors, the energy transfer mechanisms which depend on RL and PL spectra were determined. The samples excited by X-ray demonstrate characteristic luminescence peaks of Dy³⁺ (422, 480, 575, 663 and 747 nm) and Tb³⁺ (489, 544, 586, 620, 652 and 675 nm). These emissions are similar for RL and PL measurements. It could be said that the energy transfer efficiency of the host material is perfect for rare-earth ions. The synthesized phosphors exhibit various colors from yellow to blue under UV excitation. The optical band gaps of host CLW, CLW: Tb³⁺, CLW: Dy³⁺ and co-doped CLW: Tb³⁺/Dy³⁺ were calculated at values 3.83 eV, 3.44 eV, 3.64 eV and 3.52 eV, respectively. From the results obtained, the CaLa₂(WO₄)₄: Tb³⁺, Dy³⁺phosphors may be one of the potential candidates for light-emitting diode.     

Thermoluminescence response of 120 MeV Ag9+ and γ-ray exposed LiMgBO3:Dy3+ nanophosphors for dosimetry

Thermoluminescence(TL) response of LiMgBO₃:Dy³⁺ nanophosphor synthesized by combustion method was examined using γ-ray and 120 MeV Ag⁹⁺ swift heavy ion (SHI) irradiation. The LiMgBO₃:Dy³⁺ samples were exposed to 0.01 kGy −5 kGy γ-rays while for the different fluences the samples were irradiated with 120 MeV Ag⁹⁺ SHI over the range 1×10¹¹ ions cm⁻² to 1×10¹³ ions cm⁻². The prominent TL glow curve peaks appeared at 396 K and 390 K for the γ-ray and 120 MeV Ag⁹⁺ SHI irradiated samples. The glow curves for the SHI iradiated samples were more complex than those of the γ-ray exposed samples. The effect of different heating rates on the TL response was also determined. The trapping parameters (i.e. activation energy, frequency factor, order of kinetic) of all the individual peaks of the glow curves have been analysed by using Chen's formulae. The TL response curve against γ-ray exposure illustrated a good linear response upto 3 kGy and after that the response was sublinear. For the 120 MeV Ag⁹⁺ ion irradiated samples, the material exhibited a sublinear dependence against ion irradiation for the studied fluence. The good TL response against γ-ray irradiation suggested that the material can be explored for a possible application in dosimetry.     

UV–VUV spectroscopy of rare earth doped persistent luminescence materials

The electronic and defect energy level structure of polycrystalline SrAl₂O₄:Eu²⁺,R³⁺ persistent luminescence materials were studied with thermoluminescence and UV–VUV synchrotron radiation emission and excitation spectroscopy. Theoretical calculations using the density functional theory (DFT) were carried out simultaneously with the experimental work. The experimental band gap energy (E_g) value of 6.6 eV agrees very well with the DFT value of 6.4 eV. The 4f⁷ → 4f⁶5d¹ excitation bands of Eu²⁺ were found rather similar irrespective of the R³⁺ co-dopant. The trap level energy distribution depended strongly on the R³⁺ co-dopant except for the shallowest trap energy above the room temperature remaining the same, however. The different processes in the mechanism of persistent luminescence from SrAl₂O₄:Eu²⁺,R³⁺ was constructed and discussed.