Decay kinetics and thermally stimulated luminescence of Mn4+ in SrTiO3

Abstract

Decay kinetics of Mn⁴⁺ luminescence in SrTiO₃ and thermal stimulation of this luminescence (TSL) after low-temperature irradiation with light from the 355—520 nm region, have been investigated in the temperature range of 4.2—150K and 12—110K, respectively, for the first time. It is concluded that TSL glow peaks are associated with thermal release of carriers from shallow traps followed by Mn⁵⁺→Mn⁴⁺(²E) and/or Mn³⁺→Mn⁴⁺ (²E) charge transfer decay kinetics has been explained by considering trap energy levels taking part in the TSL process.     

纳米YPO4:Eu3+的合成及发光性质研究

采用水热法合成了纳米Y_1-xPO₄:xEu³⁺（005≤x≤030）系列荧光粉,并对样品进行了热处理.通过X射线衍射（XRD）、扫描电镜（SEM）等手段分析了合成样品的结构及形貌,结果表明合成的样品均为四方磷钇矿结构,在酸性和碱性条件下分别为球状和细棒状,且均在纳米尺度.研究其在真空紫外（VUV）激发下的发光性质发现,样品的激发峰最大值位于142 nm左右;与固相法的样品相比,PO^3-     

Dose dependence of thermally transferred optically stimulated luminescence signals in quartz

The thermally transferred optically stimulated luminescence (TT-OSL) responses of chemically purified fine-grained quartz from seven loess-like samples from Korea are presented. In particular, the experimental procedures used to separate the dose-dependent (recuperated OSL, ReOSL) and dose-independent parts of the signal were explored. The OSL signals used to monitor the sensitivity changes that take place during the measurement sequences used to determine the equivalent dose were investigated. A single aliquot procedure was used for the TT-OSL measurements and resulted in linear growth of the ReOSL with dose up to at least 2 kGy. For this suite of samples, a standardised growth curve (SGC) was constructed for the ReOSL, tested with dose recovery experiments, and was used to obtain D_e values for the seven samples.     

Correlation of optically and thermally stimulated luminescence of natural fluorite pellets

Natural fluorite (CaF₂), a dosimetric material of large usage, presents Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). This study examined the behavior of TL and OSL (stimulated with Blue LEDs) signals from the Brazilian natural fluorite pellets with NaCl as binding agent, as well as their correlations, in order to study and optimize the dosimetric process with this material. A series of experiments were conducted, basically with thermal treatments before OSL acquisition, and optical bleaching before TL readout. The role of NaCl in the TL and OSL emission was investigated. It was observed that natural CaF₂ TL signal is still ample to be used in dosimetric applications, as dose re-assessment in personal dosimetry after an OSL measurement. Also it was verified that the fluorite OSL signal is extinguished by a 350 °C heating and that NaCl has no contribution to the stable part of the OSL signal.     

多体系多波长计算光度法同时测定镧铈镨钕钐铕钆

本文以DBC-偶氮氯膦为显色剂,并且在显色体系中加入不同量的EDTA-Na2P2O7作为竞争配位剂,使得七组分轻稀土组分间吸收光谱灵敏度的差别逐渐加大,从而增加了轻稀土混合物体系组分间吸收光谱的线性独立性.利用数值稳定性较强的约束优化算法--可变容差法处理光谱数据,对不同浓度比例的七组分轻稀土混合物体系(La3+,Ce3+,Pr3+,Nd3+,S m3+,Eu3+,Gd3+)的测定,取得了较满意的结果.     

UV-induced photoluminescence and thermally stimulated luminescence of CaSO4:Eu and CaF2:Tb3+ phosphors

Ultraviolet radiation induced changes in photoluminescence (PL) and thermally stimulated luminescence (TSL) of europium activated calcium sulphate (CaSO₄:Eu³⁺, Eu²⁺) and terbium doped calcium fluoride (CaF₂:Tb³⁺) phosphors have been studied. PL measurements suggest conversion of Eu³⁺ to Eu²⁺ on 254 nm irradiation corresponding to charge transfer band of Eu³⁺ ions and reduction of Eu²⁺ ions with 365 nm illumination representing a f–d transition of Eu²⁺ ions. Similar studies carried out on CaF₂:Tb³⁺ phosphor, however, do not show any significant wavelength specific changes. The integrated TSL output appears to be rate-dependent for both phosphors. The wavelength dependent changes in TSL output observed for CaSO₄:Eu phosphor have been correlated with those obtained in PL studies. The changes in TSL and PL characteristics of CaF₂:Tb³⁺ phosphor have been explained on the basis of stabilisation of traps based on matrix specific charge similarities.     

Intra- and inter-configurational luminescence spectroscopy of Pr3+ -doped YPO4 nanophosphors

Nanopowders of YPO₄ phosphors with different Pr³⁺doping were successfully prepared by a sol gel method under different synthesis conditions. The crystallite size and strain show a strong dependence on the Pr³⁺ doping concentration and on the annealing temperature. By annealing at 300 °C one can obtain the xenotime structure of the pure YPO₄. The crystallite size can be controlled by controlling the annealing temperature and it increases with increasing the annealing temperature. The room temperature inter-configurational 4f² ↔ 4f5d and intra-configurational 4f²↔ 4f² emission-excitation transitions spectra are measured and investigated. Upon 4f² → 4f5d excitation transition, all the samples present broad intense emission bands attributed to 4f5d → 4f² emission transitions and peaks in red region assigned to ¹D₂→³H₄ transition as photon cascade emission phenomena (PCE). The presence of only ¹D₂→³H₄ transition is discussed. In addition, the ¹D₂ energy level lifetimes as well as the refractive indexes were determined and discussed.     

Investigating the thermally transferred optically stimulated luminescence source trap in fired geological quartz

The pre-dosed thermoluminescence (TL) emission of quartz has been found to be useful in retrospective dosimetry and archaeometry. Though the pre-dosed optically stimulated luminescence (OSL) and TL emissions have been reported to be similar, the former has been found to be un-reliable for the equivalent dose estimation. As this measurement protocol involves thermal heating at around 400 °C, the work reported in this paper investigated the influence of this heating on the OSL using fired specimens from various regions. The results suggested that the discrepancy in the behaviour of two emissions is caused by the presence of the thermally transferred optically stimulated luminescence (TT-OSL) induced by thermal-activation involved in the pre-dose treatment. This transferred signal was observed to be very significant in the case of samples containing a prominent higher-temperature TL peak at ∼375 °C. The characterization of this signal based on (i) the nature of the glow curves, (ii) thermal-annealing of the OSL trap, (iii) observation of the TT-OSL, (iv) bleaching of the source trap and (v) the correlation between TL and OSL seems to suggest that the trap corresponding to this TL peak is the source trap in the TT-OSL emission mechanism.     

UV induced photoluminescence and thermally stimulated luminescence of ThO2:Tb3+ phosphor

Thorium oxide doped with trivalent terbium ions offers itself as a novel phosphor with its photo- and thermally-stimulated luminescence (PL and TSL) characteristics showing a marked change on sustained exposure to 254 and 365 nm ultraviolet (UV) radiation. The reduction in luminescence intensity of Tb³⁺ ions, on irradiation with 254 nm photons and subsequent restoration on exposure to 365 nm, has been correlated with the complimentary behaviour in UV-induced TSL. These changes are, in turn, ascribed to inter-configurational (f–d) transitions and e–h formation and recombination processes. UV radiation induced TSL output increases linearly with incident UV radiant energy at a constant radiation flux; however, for a fixed exposure, TSL output increases with increase in radiant flux.     

YPO4∶Ho3+,Yb3+,Tm3+微纳米管的合成及上转换白光发射

水热法合成了均匀管状Tm3+,Ho3+和Yb3+三掺的YPO4微纳米管,在波长为980nm的近红外光激发下能够发射出红绿蓝三条可见光谱带以及中心波长位于795nm的近红外发射带,从而实现上转换白光发射。通过TEM,XRD和荧光光谱等表征手段对合成的Tm3+,Ho3+和Yb3+三掺YPO4微纳米管进行了结构和性能分析,结果表明,合成的YPO4微纳米管为纯净六方相,水热反应温度对荧光材料的发射光谱有较明显的影响,然而对材料物相的影响却不大。在相同反应温度下,随着掺杂稀土离子浓度的升高,相应发射峰的强度并不是单调的增强,而是由于浓度猝灭和交叉弛豫等因素呈现非单调性的变化。探讨了可能的上转换发射机制。这种上转换发射强度可调控荧光材料在三维固体显示、上转换荧光照明以及荧光探测等领域有潜在的应用。     

The study on optically stimulated luminescence dosimeter based on the SrS：Eu,Sm and CaS：Eu,Sm

With the increasing use of nuclear energy, there is a need for a wider range of efficient dosimeters for radiation detection and assessment. There has been a tremendous growth in the development of radiation detectors and devices in the past few decades. In recent years, the development of new materials for radiation dosimetry has progressed significantly. Alkaline earth sulfides （AES） have been known for a long time as excellent and versatile phosphor materials. In the present investigation, a number of phosphor samples such as mono-, binary and ternary sulfides of alkaline earths （II^a-VI^b） have been prepared and their TL properties have been studied with respect to exposure （x-ray） response and fading. In this paper, some results on SrS：Eu, Sm and CaS：Eu, Sm phosphors are presented. A type of novel OSL dosimeter is described. The dosimeter takes advantage of the characteristics of charge trapping materials SrS：Eu, Sm and CaS：Eu, Sm that exhibit optically stimulated luminescence （OSL）. The measuring range of the dosimeter is from 0.01 to 1000 Gy. The OSL dosimeters provide capability for remote monitoring radiation locations which are difficult to access and hazardous. This equipment is relatively simple, small in size and has low power consumption. The device is suitable for space radiation dose exploration. In addition, it also can be used in IC and other radiation occasions and has good prospects.     

The synthesis and afterglow luminescence properties of a novel red afterglow phosphor: ZrO2:Sm3+,Sn4+

A novel ZrO₂:Sm³⁺,Sn⁴⁺ phosphor is synthesized by solid state reaction. The ZrO₂:Sm³⁺ does not show afterglow. But, after doping Sn⁴⁺, intense red afterglow luminescence is firstly observed in ZrO₂:Sm³⁺,Sn⁴⁺ and it can last more than 1000 s at maximum. The afterglow decay curves of ZrO₂:Sm³⁺,Sn⁴⁺ are fitted by three exponential components and the decay process consists of initial fast, intermediate and slow decay. The thermoluminescence indicates that the Sn⁴⁺ ions induce suitable traps with the depth of 0.436 eV and result in efficient afterglow luminescence of ZrO₂:Sm³⁺,Sn⁴⁺. The thermoluminescence filling and fading experiments further confirm the important role of the proper shallow traps induced by doping Sn⁴⁺ on the afterglow of ZrO₂:Sm³⁺,Sn⁴⁺.     

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.     

Sm3+在玻璃中的发光以及Sb6+、Ce6+、Gd3+对Sm3+发光性质的影响

本文研究了单掺(Sm3+,Ce3+、Gd3+.Sb3+、双掺(Sm3++Ce3+、Sm3++Gd3+,Sm3++Sb3+)和兰掺(Sm3++Gd3++Ce3+)约四十余种不同玻璃的发射谱和激发谱.探讨了玻璃成份和掺杂离子浓度对Sm3+发光性质的影响以及Ce3+,Gd3+、Sb3+、Ce3++Gd3+对Sm3+的敏化作用。     

下转换材料β-NaYF4:Tb3+,Yb3+的水热法合成和发光性质研究

利用水热法合成了粉末发光材NaYF4:Tb3+,Yb3+分别用X射线衍射(XRD),光致发光谱(PL)和激发谱(PLE)测试了合成材料的物相结构和发光性质.研究结果表明:合成的NaYF4:Tb3+,Yb3+抖材料为六方相的品体,无立方相的.改变Tb3+和Yb3+的掺杂浓度后品格结构没有变化,说明离子Tb3+和Yb3+取...     

Phototransferred effects in TLD-500 luminescent detectors and their correlation with thermally and optically stimulated luminescence responses

The results from studies on the correlation between thermally and optically stimulated luminescence (OSL) responses and the kinetics of charge carrier phototransfer in corundum-based TLD-500 detectors are presented. It is shown that the fast component of the OSL decay curve is related to the depletion of the main trap, while the slow component is associated with the phototransfer process. The effect of preliminary heating on the behavior of OSL decay is studied.     

Low-temperature luminescence and thermally stimulated luminescence of BeO: Mg single crystals

Luminescence and thermally stimulated luminescence (TL) of BeO: Mg crystals are studied at T = 6–380 K. The TL glow curves and the spectra of luminescence (1.2–6.5 eV), luminescence excitation, and reflection (3.7–20 eV) are obtained. It is found that the introduction of an isovalent magnesium impurity into BeO leads to the appearance of three new broad luminescence bands at 6.2–6.3, 4.3–4.4, and 1.9–2.6 eV. The first two are attributed to the radiative annihilation of a relaxed near-impurity (Mg) exciton, the excited state of which is formed as a result of energy transfer by free excitons. The impurity VUV and UV bands are compared with those for the intrinsic luminescence of BeO caused by the radiative annihilation of self-trapped excitons (STE) of two kinds: the band at 6.2–6.3 eV of BeO: Mg is compared with the band at 6.7 eV (STE₁) of BeO, and the band at 4.3–4.4 eV is compared with the band at 4.9 eV (STE²) of BeO. In the visible region, the luminescence spectrum is due to a superposition of intracenter transitions in an impurity complex including a magnesium ion. The manifestation of X-ray-induced luminescence bands at T = 6 K in BeO: Mg indicates their excitation during band-to-band transitions and in recombination processes. The energy characteristics of the impurity states in BeO: Mg are determined; the effect of the isovalent impurity on the fluctuation rearrangement of the BeO: Mg structure in the thermal transformation region of STE₁ → STE₂ is revealed.