Mechanisms of Fluorescence Quenching of Pr^(3+)-Doped PbWO_4 Crystal

Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the ^3P0 and ^1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the ^1D2 manifold and the cross-relaxation of dlpole-dipole interaction was confirmed. Consequently, the ^3p0 manifold is more favorable as an upper laser level than the ^1D2 manifold.

Light Yield Measurements for PbWO_4 Crystals by Single Photoelectron Method

The measurements of light yield of PbWO4 crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with normal radioactive sources is proposed and the measurements for severalPbWO4 samples produced by Beijing Glass Research Institute are reported.

Improvement on the Luminescence Property of Y, Sb Co-doped PbWO_4 Single Crystal

The effect of Y and Sb co-doping on the luminescence property of PbWO 4 crystals has been investigated. Compared with undoped PbWO4, the transmittance and emission peak intensity of Y∶Sb∶PbWO 4 crystals were obviously improved. In addition, its transmittance cutoff wavelength and emission peak shifted to the shorter one. The mechanism of effect of Y and Sb on the transmittance spectra was briefly discussed. The light yield of Y∶Sb∶PbWO 4 crystals was 25p.e./MeV, which was two times of that of undoped PbWO 4. Our experiments showed that Y and Sb co-doping was a selectable method to improve the luminescence property of PbWO 4.

Tailoring crystal plane of short-process regenerated LiFePO_(4) towards enhanced rate properties

Captured by the environmental and economic value,the recycling of spent lithium iron phosphate(LFP)batteries has attracted numerous attentions.However,hydrometallurgical method still suffers from complex process,and hydrothermal method is limited by morphology control,ascribed to the strong polarity of water.Herein,supported by ethanol as crystal surface modifier,the regular(010)orientation and short b-axis are effectively tailored for regenerated LFP.As Li-storage cathode,the capacities of as-optimized LFP could reach up to 157.07 mA h g^(-1)at 1 C,and the stable capacity of 150.50 mA h g^(-1)could be remained with retention of 93.48%after 400 cycles at 1 C.Even at 10 C,their capacity could be still kept about 119.3 m A h g^(-1).Assisted by the detail analysis of adsorption energy,the clear growth mechanism is proposed,the lowest adsorbing energy(-4.66 eV)of ethanol on(010)crystal plane renders the ordered growth along(010)crystal plane.Given this,the work is expected to shed light on the tailoring mechanism of internal plane about regenerated materials,whilst providing effective strategies for highperformance regenerated LFP.

Enhancing the crystallinity and stability of perovskite solar cells with 4-tert-butylpyridine induction for efficiency exceeding 24%

Perovskite solar cells(PSCs)have emerged as a promising photovoltaic technology because of their high light absorption coefficient,long carrier diffusion distance,and tunable bandgap.However,PSCs face challenges such as hysteresis effects and stability issues.In this study,we introduced a novel approach to improve film crystallization by leveraging 4-tert-butylpyridine(TBP)molecules,thereby enhancing the performance and stability of PSCs.Our findings demonstrate the effective removal of PbI_(2)from the perovskite surface through strong coordination with TBP molecules.Additionally,by carefully adjusting the concentration of the TBP solution,we achieved enhanced film crystallinity without disrupting the perovskite structure.The TBP-treated perovskite films exhibit a low defect density,improved crystallinity,and improved carrier lifetime.As a result,the PSCs manufactured with TBP treatment achieve power conversion efficiency(PCE)exceeding 24%.Moreover,we obtained the PCE of 21.39%for the 12.25 cm^(2)module.

Mitigating kinetic hindrance of single-crystal Ni-rich cathodes through morphology modulation,nickel reduction,and lithium vacancy generation achieved by terbium doping

Single crystallization has proven to be effective in enhancing the capacity and stability of Ni-rich LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(SNCM)cathode materials,particularly at high cut-off voltages.Nevertheless,the synthesis of high-quality single-crystal particles remains challenging because of severe particle agglomeration and irregular morphologies.Moreover,the limited kinetics of solid-phase Li^(+)diffusion pose a significant concern because of the extended diffusion path in large single-crystal particles.To address these challenges,we developed a Tb-doped single-crystal LiNi_(0.83)Co_(0.11)Mn_(0.06)O_(2)(SNCM-Tb)cathode material using a straightforward mixed molten salt sintering process.The Tb-doped Ni-rich single crystals presented a quasi-spherical morphology,which is markedly different from those reported in previous studies.Tb^(4+)oping significantly enhanced the dynamic transport of Li^(+)ions in the layered oxide phase by reducing the Ni valence state and creating Li vacancies.A SNCM-Tb material with 1 at%Tb doping shows a Li^(+)diffusion coefficient up to more than 9 times higher than pristine SNCM in the non-diluted state.In situ X-ray diffraction analysis demonstrated a significantly facilitated H1-H2-H3 phase transition in the SNCM-Tb materials,thereby enhancing their rate capacity and structural stability.SNCM-Tb exhibited a reversible capacity of 186.9 mA h g^(-1)at 5 C,retaining 94.6%capacity after 100 cycles at 0.5 C under a 4,5 V cut-off.Our study elucidates the Tb^(4+)doping mechanisms and proposes a scalable method for enhancing the performance of single-crystal Ni-rich NCM materials.

Surface deterioration dependent on the crystal facets of spinel LiNi_(0.5)Mn_(1.5)O_(4) cathode active material

The spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode active materials(CAMs)are considered a promising alternative to commercially available cathodes such as layered and polyanion oxide cathodes,primarily due to their notable safety and high energy density,particularly in their single-crystal type.Nevertheless,the industrial application of the LNMO CAMs is severely inhibited due to the interfacial deterioration and corrosion under proton-rich and high-voltage conditions.This study successfully designed and synthesized two typical types of crystal facets-exposed single-crystal LNMO CAMs.By tracking the electrochemical deterioration and chemical corrosion evolution,this study elucidates the surface degradation mechanisms and intrinsic instability of the LNMO,contingent upon their crystal facets.The(111)facet,due to its elevated surface energy,is found to be more susceptible to external attack compared to the(100)and(110)facets.Our study highlights the electrochemical corrosion stability of crystal plane engineering for spinel LNMO CAMs.

Analyses of Reaction Mechanisms among Different Sulfonation Reagents and m-Diphenylamine and Crystal Structures of the Formed Compounds

In the traditional process, m-phenylenediamine reacts with fuming sulfuric acid at high temperature to get intermediates, and then after dehydration occurs intramolecular rearrangement to get 2,4-diaminobenzenesulfonic acid. Traditional methods need to consume a lot of fuming sulfuric acid or concentrated sulfuric acid, resulting in high industrial large-scale production cost, more waste, and posing a serious environmental pollution risk. In this thesis, three different sulfonation reagents were used for the sulfonation reaction of m-phenylenediamine, and the reaction mechanisms and crystal structures of the three pathways were investigated. The three routes are: 1) one-step synthesis of monosulfonated compound 1 from raw material and sulfur trioxide (SO3);2) rapid reaction of raw material and chlorosulfonic acid to synthesize bisulfonated compound 2;3) direct eutectic crystallization of raw material and ordinary sulfuric acid to obtain compound 3. The crystal structure of the compounds synthesized by three paths was analyzed by X-ray single crystal diffraction, and compound 1 was characterized by NMR, Fourier infrared spectra, UV-visible spectrum and Mass spectrometry. The one-step synthesis of SO3 as a sulfonation reagent has the advantages of mild reaction conditions, simple operation and low cost.

用正电子湮没实验研究PbWO_4新型闪烁晶体绿光发光机理

通过正电子湮没寿命谱研究了PbWO_4晶体退火处理前后缺陷的变化；发现氧退火后，晶体正电子寿命值τ_2变小，正电子捕获率κ增大，真空退火反之。并且PbWO_4晶体氧退火后发光主峰位从440nm移到485nm的绿光处，而真空退火晶体发射谱谱形并未变化。从不同退火处理对晶体的影响，提出了PbWO_4晶体中铅空位形成WO_3＋O^-发绿光的发光模型。

PbWO_4闪烁晶体的发光动力学模型

在对PbWO4闪烁晶体的光谱特性、发光衰减及其温度依赖以及热释光的研究基础上,并结合理论计算,提出了PbWO4晶体发光的动力学模型,给出了PbWO4晶体的基本能带结构及激子发光中心能态、陷阱能级在能隙中的位置。用此模型可以完整说明PbWO4的发光过程,特别是导致室温下发光效率低的原因。最后还对其主发射成分蓝、绿发光中心的起源作了简要讨论。

高光产额钨酸铅(PbWO_4)晶体的研究进展

钨酸铅(PbWO4 )晶体由于具有高密度、短辐照长度、高的辐照硬度和快发光等特点而成为目前最具发展潜力的闪烁晶体之一,但其光产额低的缺点限制了它在高能领域以外的应用。因此,提高钨酸铅晶体的光产额以使其在PET装置等低能领域获得应用已成为近年来钨酸铅晶体的研究热点。本文综述了高光产额钨酸铅晶体的研究现状,指出了目前存在的问题。结合理论分析,提出采用坩埚下降法晶体生长技术,离子掺杂和退火等措施是进一步提高钨酸铅晶体光产额的主要途径。

掺Sb对PbWO_4晶体发光性能的改善

首次报道了ＰｂＷＯ４：Ｓｂ的光谱特性，包括透射谱和Ｘｅ灯光源激发的发射谱与激发谱．掺Ｓｂ具有增强绿光带、抑制红光带并大幅度提高光产额的效果．通过与空气退火ＰＷＯ发光的比较，对绿光带的起因、Ｓｂ掺杂的作用也进行了简要的讨论．

不同气氛退火对PbWO_4单晶发光的影响

通过对不同气氛条件下退火的PbWO4（PWO）单晶样品的激发谱与发射谱的对比研究,发现真空退火从整体上抑制PbWO4的发光强度,氧空位（Vo）缺陷是420nm吸收和红光发射的原因,而空气退火可以有效抑制Vo缺陷,全面改善PWO的发光性能。另外,首次报道了310nm附近的激子激发峰发生劈裂的现象,其中波长较长的320nm激发对应于与Vo缺陷相关的激子激发态。

新型闪烁晶体PbWO_4的研制

报道了PbWO_4晶体的生长,研究了原料的纯度以及晶体生长工艺对晶体质量的影响,测试了晶体的光学性能和闪烁性能,生长出优质的PbWO_4晶体。

下降法生长的PbWO_4晶体中黄色芯的形成及消除

本文报道了以ＷＯ３和ＰｂＯ粉末为原料采用改进的Ｂｒｉｄｇｍａｎ法长的ＰｂＷＯ４晶体中的黄色芯。借助于电子探针和Ｘ射线粉末衍射仪对黄色芯进行了研究，发现黄色芯主要为Ｐｂ２ＯＷ５和ＷＯ３颗粒。分析了产生黄色芯的原因，提出了消除此种宏观缺陷的一些措施。

Bridgman法生长的PbWO_4晶体的腐蚀观察

利用光学显微镜观察了Bridgman法生长的PbWO4晶体 (0 0 1)晶面的腐蚀形貌 ,讨论了位错蚀坑的形态特征 ,分布规律以及与晶体结晶习性的关系 ,同时还观察了亚晶界的形态 。

PbWO_4晶体光学性能的结构效应

本文针对人工合成PbWO4 晶体的结构特征 ,测试了晶体沿 [10 0 ]与 [0 0 1]方向的光学透射谱、发射光谱以及发光效率 ,详细地讨论了PbWO4 晶体显著的光学各向异性效应 。

Cd∶PbWO_4晶体的生长及其性质

采用提拉法生长了Ｃｄ∶ＰｂＷＯ４晶体，最佳生长工艺参数：液面上和液面下轴向温度梯度分别为４０～５０℃／ｃｍ和１７～２５℃／ｃｍ，生长速度２～３ｍｍ／ｈ，转速为２５～３０ｒ／ｍｉｎ，以这一条件生长晶体可克服液流转换，避免由此引起的缺陷。Ｃｄ∶ＰｂＷＯ４的透过率明显高于各类型未掺杂ＰｂＷＯ４晶体，测得Ｃｄ∶ＰｂＷＯ４的发光效率为２１．２ｐ．ｅ／ＭｅＶ，而高纯ＰｂＷＯ４为１０．５ｐ．ｅ／ＭｅＶ，分析纯退火ＰｂＷＯ４为８．２ｐ．ｅ／ＭｅＶ，未退火ＰｂＷＯ４为６．７ｐ．ｅ／ＭｅＶ。Ｃｄ∶ＰｂＷＯ４晶体的平均衰减时间约为１０ｎｓ。以上结果表明。

PbWO_4:Y晶体性能特性的研究

为了满足西欧核子研究所 (CERN)的要求 ,我们结合生长的PbWO4晶体的性能特点 ,首次单掺了稀土元素钇 (Y) ,一定程度上提高了PbWO4晶体的光输出及抗辐照损伤性能。我们的研究结果主要表现在下面几个方面 :在同一Bridgman法生长炉中 ,我们进行了Y元素不同掺杂质量分数 2 .5× 1 0 -3 % ,1×1 0 -2 % ,2× 1 0 -2 % ,3× 1 0 -2 % ,4× 1 0 -2 %的试验。生长所得PbWO4晶体 ,加工成 2 2mm×2 3mm× 2 30mm× 1 5mm× 2 6mm尺寸 ,分别测其光输出。在12 7Cs源激发下 ,用R1 847S型光电倍增管接收PbWO4晶体闪烁脉冲信号 ,通过放大器对电信号放大 ,在微机多道仪上得出发光能谱。测试结果表明掺入Y质量分数 2 .5× 1 0 -3 %晶体光输出较纯PbWO4晶体变化不大 ,当掺至质量分数为 1× 1 0 -2 %时 ,晶体光输出在一定程度上有了提高 ,但随着Y掺入质量分数增至3× 1 0 -2 %后 ,晶体光输出又逐步降低。取以上晶体经Co源辐照 35rad/h× 70h后 ,再测其光输出。光输出与辐照前光输出之比值大小就可衡量晶体抗辐照损伤性能的好坏。实验数据表明掺入一定量Y晶体的抗辐照损伤性能有一定提高 ,且在一定量的范围内随Y的增加 ,抗辐照损伤性能也随之提高。同一晶体沿轴向取几段做GDMS分析 ,分析表明Y在PbWO4晶体中分布较均匀 ,即分?

掺镁PbWO_4晶体的生长及其闪烁性能研究

用Ｃｚｏｃｈｒａｌｓｋｉ法生长了掺镁ＰｂＷＯ４晶体，测试了Ｍｇ：ＰｂＷＯ４晶体的透射光谱、激发发射光谱、发光效率和衰减时间。Ｍｇ：ＰｂＷＯ４晶体的透过率和发光效率高于Ｐｂ－ＷＯ４晶体。