Optical properties of Eu-activated calcium aluminosilicates synthesized in different atmospheres

The optical properties of Eu-activated CaAl₂Si₂O₈ appear to be totally dependent on the atmosphere during the synthesis processing. Compared with oxidizing/reducing-sintered samples, a significant enhancement in both the photoluminescence and afterglow for the vacuum-sintered sample is observed. The deficiency of energy transfer among the different emission centers is the prevailing contribution to the highest photoluminescence intensity of the vacuum-sintered sample. A distinction in afterglow characteristics of CaAl₂Si₂O₈:Eu prepared in different atmosphere is suggested to be mainly due to the distribution of different trap depths at three types of emission centers.     

Electron paramagnetic resonance study of rare-earth related centres in K2YF5:Tb thermoluminescence phosphors

Rare-earth related centres have been investigated in K₂YF₅:Tb³⁺ crystals, exhibiting thermoluminescence (TL) below and above room temperature (RT), using electron paramagnetic resonance (EPR) spectroscopy at Q (34 GHz) and W-band (94 GHz). The spectra have been studied prior to irradiation, after exposure in the kGy range to X-rays at 77 K and subsequent pulse annealing up to 570 K. In addition to Gd³⁺, previously studied in detail, we identified Er³⁺ and Yb³⁺ centres as accidental impurities in as-grown crystals and determined their effective g tensors. The EPR spectra of irradiated and annealed crystals provide evidence for the production of at least three distinct Tb-related trapped hole centres, two of which could definitely be identified as Tb⁴⁺. Hence, we prove that the Tb³⁺ activator ions also act as hole traps in K₂YF₅. Pulse annealing experiments indicate that the TL above RT results from thermal release of electrons, recombining at these Tb⁴⁺ ions.     

Spectral and kinetic characterization of orange-red emitting Sr3Al2O6:Eu/Smphosphor

We report, for the first time Sm³⁺ doped nanocrystalline Sr₃Al₂O₆ phosphor. Effect of Eu³⁺ doping in the present host is also studied. XRD results match with standard data from JCPDS file confirming cubic structure with Pa3 space group. PL Maximum for Eu/Sm is obtained at 590 nm and 573 nm respectively, and corresponds to orange-red region of electromagnetic spectrum. Morphology of combustion synthesized powder is platelet, while for calcined powders, cubic shaped crystallites are obtained. Information on various trapping parameters is obtained from thermally stimulated Luminescence (TSL) studies. Non-shifting T_m property is applied to define the order of kinetics and is thereafter assumed as 1. T_m − T_stop procedure and repeated initial rise method are applied to estimate apparent activation energies and peak positions. Further, chi-square minimization procedures via computerized glow curve deconvolution (CGCD) technique provide best-fit results. The figure of merit for deconvoluted Eu and Sm doped samples are 0.48% and 0.67% respectively. The apparent activation energies for Eu doped samples are 0.89 eV, 1.05 eV, 1.30 eV, while, for Sm doped samples, the activation energies are 0.84 eV and 1.06 eV. Persistence behavior of the present phosphor is attributed to contribution due to shorter and longer components as are obtained during phosphorescence decay studies. In both the cases; probability of recombination is more in comparison to the retrapping within a quasi continuous framework of trapping sites.     

Rare-earth doped sol-gel derived oxyfluoride glass-ceramics: Structural and optical characterization

Glass-ceramics containing RE³⁺-doped BaF₂ nanocrystals (RE = Eu, Sm, Dy, Ho and Pr) with the size below 10 nm size have been made by using the controlled crystallization at higher temperatures of the RE³⁺-doped SiO₂-BaF₂ xerogels. Photoluminescence measurements have indicated the incorporation of the RE³⁺ ions in both silica network and in the BaF₂ nanocrystals. Thermoluminescence measurements have shown a peak whose position depends on the nature of RE³⁺-dopant as it follows: 140 °C (for Ho³⁺, Dy³⁺), 340 °C (for Sm³⁺) and 370 °C (for Eu³⁺); in Eu³⁺-doped SiO₂ glass the TL peak is shifted to 383 °C. The peaks in glass-ceramics were assigned to the recombination of the electrons thermal released from the RE³⁺-electron traps located in both glass-matrix and BaF₂ nanocrystals. Within the series the trivalent lanthanide ions act as increasingly deeper electron trapping centres.     

微量杂质在BGO Bridgman生长和性质上的行为

在 Bridgman 生长的 BGO 闪烁单晶中,含量为 10~(-4)～10~(-6)wt%的 Fe、Pb、Cr、Mn、Co、Ni、Cu、Al 等微量杂质主要来源于原料和工艺过程中的局外污染。铂从坩埚上被侵蚀进入 BGO 熔体,其含量<2×10~(-5)wt%。用 AAS 和 ICP 分析测定了 Bridgman 生长中微量杂质的有效分凝系数。过渡金属杂质,特别是 Fe,使 BGO 染色并引起辐照损伤,形成300～700nm 范围的强吸收谱,致使 BGO 单晶的能量分辨率、相对荧光输出下降约10—20%。在辐照损伤下形成的 Fe、Pb 杂质色心,受热时形成晶体的热发光。     

热释光法用于中国古陶辨伪鉴定(英文)

本文叙述的方法是对一般的碎陶片进行断代的方法的改进,对陶器损害小,但结果仍相当精确。在过去几年中成功地分析了31个样品,大部分样品的年龄估计为1100—4500年,其中已有19个样品被证明与实际年龄相符。叙述了分析的一般程序和所遇到的问题。     

Study of the luminescent properties of KMgF3:Sm

The photoluminescence (PL), radioluminescence (RL) and thermoluminescence (TL) of KMgF₃ doped at several Sm concentrations have been investigated. The maximum TL and RL yield under beta irradiation has been observed in KMgF₃:Sm 0.02 mol%. The glow curve of this doped perovskite is made up of at least five peaks located at 95, 120, 160, 270, and 330 °C. The third peak appears to be the most convenient for personal or environmental dosimetry, since it shows no fading and good linearity within the investigated dose range (0.020-200 Gy). From the RL and PL spectra it has been found that most of KMgF₃:Sm emission is located at wavelengths higher than 650 nm. This emission, which is characteristic of Sm²⁺, makes this doped compound attractive for fiber-optic dosimetry.     

小江断裂沿线低阶地面热释光年代学标尺的研究

用ＴＬ测年技术测定了沿小江断裂发育的主要河流低阶地沉积物的堆积年龄,结合毗邻地区同级阶地沉积物的堆积年代,估算了研究区低阶地面的形成时代,为建立研究区最新气候,构造事件的序列提供年代学依据。     

VUV spectroscopy and low temperature thermoluminescence of LSO:Ce and YSO:Ce

Radioluminescence and UV-excited photoluminescence spectra, photoluminescence time profiles, thermoluminescence glow curves and gamma-excited energy spectra (determining scintillation light yields) of several Lu₂SiO₅:Ce and Y₂SiO₅:Ce samples were recorded. The results are analyzed with attention focused on possible correlations between trap distributions, VUV responses, and light yields. The aspect of two distinct sites occupied by Ce³⁺ ions is also discussed.     

A novel bifunctional Dy3+ activated RbCaF3 single phase phosphor: Facile synthesis and dual-luminescence properties for WLEDs and dosimetry applications

A series of Dy³⁺ activated RbCaF₃ phosphors was synthesized by the conventional high temperature solid state reaction technique under ambient atmosphere. The structural properties and morphology of synthesized compounds were analyzed by PXRD and FE-SEM, respectively. The chemical composition of synthesized phosphors was obtained by EDAX. The phosphor was excited at 386 nm and monitored at 484 and 574 nm, and the strongest peak was located at 484 nm (blue region). In addition, the point of RbCaF₃:Dy³⁺ with calculated chromaticity coordinates in the CIE diagram was located in the yellow region. TL characteristics of the RbCaF₃:Dy³⁺ phosphor was analyzed and the glow curve peak was emitted at 355 K. The symmetry factor, Balarin parameter, activation energy and frequency factor were calculated by Chen method from the TL glow curve, and the TL signal degradation was also analyzed.