电注入着色氟化钡晶体F色心的扩散激活能

在8组不同的温度和电压条件下,用自行设计的电注入实验装置对氟化钡晶体进行点阴极电注入着色.测试和分析了电注入着色前后氟化钡晶体的吸收光谱.研究结果表明:电注入着色后氟化钡晶体中产生了大量F色心.电注入过程中,F色心首先在阴极注入点附近产生,然后逐渐向阳极扩散.通过测试晶体着色深度并利用F色心迁移率与温度的关系确定出了电注入着色氟化钡晶体中F色心的扩散激活能.     

电注入着色溴化钾晶体光谱特性及激活能

利用电注入着色装置,分别使用点阴极与平板阳极和点阳极与平板阴极在不同条件下对溴化钾晶体进行电注入着色.点阴极注入时,在着色晶体中产生V色心和F色心,计算得到F色心激活能0.84 eV.点阳极注入时,在着色晶体中产生V色心,计算得到V色心激活能0.49 eV.对着色晶体进行系统的光谱测量,确定色心光谱吸收带的光谱参数.对比两种情况下测得的电流～时间关系曲线,解释其色心形成机理.     

点阳极电注入氯化钠晶体光谱特性及机理

利用电注入着色装置,使用点阳极和平板阴极在不同条件下对氯化钠晶体进行电注入着色.在着色晶体中产生大量V、F、胶体C和N心.对着色晶体进行系统的光谱测量,确定色心光谱吸收带的光谱参数.研究不同注入条件对色心浓度的影响.测得电流～时间关系曲线.计算出V色心的激活能小于F色心激活能,进而解释色心形成机理.     

氧化镁晶体电注入着色及光谱特性

用自行研制的电注入装置,在不同条件下对氧化镁晶体进行电注入并使之有效着色.在着色晶体中有效地产生大量F、F2和一些未知色心,并探讨了色心形成机理.对着色氧化镁晶体进行了系统光谱测量,确定这些色心的吸收光谱带光谱参数,并对色心形成过程进行分析.结果表明,随着电压的升高,通电时间增长,色心的浓度增大,电注入仅经单步过程,便可获得以往采用其他着色方法多步处理才能产生的多种类色心,更具实用性.     

氯化钠晶体电注入着色机理解释

用自行研制的电注入装置,在不同温度下对氯化钠晶体进行电注入并使之有效着色。在着色晶体中有效地产生大量F、胶体C、N和一些未知色心,给出色心形成机理。对着色氯化钠晶体进行了系统光谱测量确定出这些色心的吸收光谱带光谱参数。借助测得的电流和时间关系图,对经此种电注入着色晶体中色心形成提出机理解释。实验结果表明,电注入仅经单步过程,便可获得比以往采用其他方法着色并需经多步处理才能产生的多种类色心,更具实用性。     

溴化钾晶体电注入着色临界温度及机理

用自行研制的电注入装置,对溴化钾晶体进行电注入并使之有效着色.由基本理论可以得出溴化钾晶体电注入着色临界温度理论值为598 K,并依此拟定和实施具体实验方案.通过实验进行得到电注入着色临界温度实验值为603 K.达到临界温度后,溴化钾晶体被着色,产生F色心.研究结果表明,临界温度理论值与实验值符合得很好.借助测得的电流～时间关系图,对经此种电注入着色晶体中色心形成提出机理解释.     

电注入着色氯化钠晶体光谱特性及激活能

用自行研制的电注人装置,在不同条件下对氯化钠晶体进行电注人并使之有效着色.在着色晶体中有效地产生大量F、胶体C和N心,并研究了色心形成机理.对着色氯化钠晶体进行了系统光谱测量确定出这些色心的吸收光谱带光谱参数.通过计算得到氯化钠晶体F色心激活能为0.97eV.     

氙离子注入氯化钾和溴化钾晶体光谱特性

用36keV氙离子注入,有效地使氯化钾和溴化钾晶体着色.在室温下,对着色晶体进行系统光谱分析.在着色晶体中,观测到大量F、R、M和未知色心,并给出色心生成与转化机理.用解谱的方法,分别从着色氯化钾和溴化钾晶体吸收光谱中合理地分解出K、F、R、M和一些其它吸收带,并精确确定这些吸收带的光谱参数.     

NV色心浓度与退火温度的Boltzmann模型

金刚石NV色心具有室温可观测到的零声子线,发光稳定,相干时间长等优秀的光学特性,可实现高精度的物理量探测和量子调控.其中,NV色心的浓度是影响其宏观性能和应用的关键因素之一.这项研究分析了不同退火温度下金刚石NV色心的荧光光谱,研究了两种不同电子注入剂量下NV色心浓度与退火温度的关系.首先,通过电子辐照,高温退火等技术制备了含有不同浓度NV色心的金刚石样品.然后测量分析了不同制备条件下NV色心的荧光光谱,求得了其声子带的总荧光强度来表征NV色心浓度.分析了NV色心浓度与退火温度的关系,根据不同温度范围NV色心浓度的变化情况提出了抑制区、扩散区和饱和区三个分区.根据实验数据拟合得到了NV色心浓度与退火温度的玻尔兹曼模型,并得到了在780℃附近NV色心浓度的变化速率最快.     

硼、氮共掺杂金刚石的高温高压退火研究

本文通过温度梯度法在5.5 GPa和1300℃的条件下合成了硼、氮共掺杂金刚石单晶.随后分别在5.0 GPa,2000℃和2100℃的条件下对合成金刚石进行了高温高压(HPHT)退火处理.傅里叶红外光谱(FT-IR)测试表明高温高压退火后晶体内部单一替代形式的C心氮转变成了聚集态A心氮,且随着退火温度的升高A心氮的含量提高.晶体内部带正电荷的氮离子N+的含量并未受到退火处理的影响.经过高温退火后晶体内部出现了NV0和NV-色心,但是继续提高退火温度时NV色心消失.高温高压退火并未对金刚石晶体的结构及内应力产生明显的影响.高温高压退火处理后金刚石晶体的热稳定性能提高,其起始氧化温度、剧烈氧化温度以及质量急剧减少的温度点分别提高了65℃、55℃以及61℃.本文对高温高压退火处理应用到硼、氮共掺杂金刚石提供了指导.     

Role of oxygen vacancies in the coloration of 0.65Pb(Mg1/3Nb2/3)O3‐0.35PbTiO3 single crystals

The coloration and oxygen vacancies in 0.65Pb(Mg_1/3Nb_2/3)O₃‐0.35PbTiO₃ (PMN‐PT(65/35)) (starting composition) single crystals grown by a so‐called modified Bridgman technique were investigated in this paper. Light yellow and dark brown colored crystals were generally observed for the typical as‐grown PMN‐PT(65/35) single crystals. X‐ray diffraction results demonstrated that they were both of pure perovskite structure, but good electric properties were only obtained for the light yellow crystal. X‐ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure of its components. The O 1s photoelectron spectra of the dark brown colored crystals located at the higher binding energy side, which meant the existence of the more oxygen vacancies. It accordingly led to the formation of the low valence cations associated with the coloration of the crystals, which is also testified by the obtained X‐ray photoelectron spectra of Ti and Nb. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of drawing temperature on the strength of fluoride glass fibers

The tensile strength of fluorozirconate glass fibers was measured as a function of fiber drawing temperature, and strengths ranging from 60–220 MPa were observed. Statistical analysis of the strength data points to a bimodal behavior in the fibers drawn at high temperatures, while the mode of fracture is essentially unimodal for fibers drawn at lower temperatures. SEM examination of the fibers drawn at high temperatures revealed the presence of crystals in the fibers, and these crystals were associated with flaws which gave rise to the observed low strength distribution.     

掺钕KGW激光晶体的各向异性吸收光谱及其上转换发光

在室温下测量了掺钕钨酸钾钆(Nd3 ∶KGW)晶体三个晶轴方向的吸收光谱,其吸收谱带强度明显显示各向异性。将Judd-O felt(J-O)理论进行修正,使其扩展应用于处理各晶轴方向的吸收光谱,计算出三个晶轴方向的各光谱带吸收系数、电偶极跃迁振子强度,其结果说明了Nd3 :KGW吸收光谱存在着各向异性。同时还研究了该材料在812nm激发下的上转换荧光特性,观察到较强的蓝色荧光。     

Synthesis, X-ray and neutron diffraction and Mössbauer studies of SrFeOx crystals

Tetragonal single crystals of the nonstoichiometric strontium ferrate with the lattice parameters a = 3.8525(3) and c = 3.8781 (3) Å have been synthesized for the first time by the method of floating-zone melting in the SrFeO_x system. The neutron diffraction patterns of the crystals showed weak additional reflections indicating the formation of the superstructure with double spacing along the [hh0] direction. The Mössbauer spectra of the crystals were obtained and measured in the temperature range 80–300 K. It was established that below the temperature T _N = 232(1) K, the crystals are in the magnetically ordered state with 3/5 of iron ions being in the trivalent state and all the remaining iron ions in the tetravalent state. This leads to the crystal composition SrFeO_2.71. The electric resistivity of the crystals equal to 100 ω cm at room temperature drastically decreases at temperatures exceeding 470 K.     

The temperature gradient technique (TGT) growth and optical properties of Yb-doped YAlO3 single crystal

The dark-brown colored 5 at% Yb-doped YAlO₃ (Yb:YAP) single crystal was grown successfully by temperature gradient technique (TGT) for the first time. The TGT-grown Yb:YAP crystal with the perovskite structure and excellent crystallization perfection were confirmed by the X-ray diffractions techniques. The dark-brown color of TGT-Yb:YAP crystal turned into the colorless after annealing in the air at 1200 °C for 10 h. The absorption spectra, LD-excited infrared emission and X-ray excited luminescence spectra of the air-annealed Yb:YAP single crystal were investigated at the room temperature. The results indicate that the TGT-Yb:YAP single crystals can be used for the laser and scintillation applications.     

Commentary on ‘Nonlinear impedance as possible result of ion-polaron interaction in Cu2O-Al2O3-SiO2 glass’

Recently, Barczynski [J. Non-Cryst. Solids 356 (2010) 1962] published nonlinear impedance spectra of a copper aluminosilicate glass which conducts both ions and polarons. Nonlinearities in the impedance signal were detected at electric field strengths as low as 1 V/mm. In order to rationalize this finding, a qualitative picture was suggested with coupled movements of ions and polarons in the bulk of the glass. A closer inspection of the nonlinear spectra reveals, however, that the nonlinearities occur exclusively in the electrode polarisation regime of the impedance spectra and are therefore not related to bulk charge transport.     

Crystallization of proteins under an external electric field

An external electric field affects the crystallization of proteins when applied under some conditions of temperature, pH, and precipitating agent composition. As suggested in the theoretical part of this paper, it produces large protein concentration gradients inside the mother liquor leading to a local supersaturation area in the crystallization solution. Such an experiment has been used for the first time on the crystallization of a protein. The effects of an external electric field on the crystallization of hen egg-white lysozyme at 293 K, pH 4.5, and two NaCl concentrations (0.6–0.7 M) have been investigated using the vapor diffusion method. The application of electric field results in a smaller number of crystals with larger size. The crystals grew at the droplet surface, near the cathode. The nucleation rate is drastically reduced and this experimental method could be used to control the number of crystals in the droplet.     

Effect of an External Electric Field on Electronic Excitation Energy Transfer in Molecular Crystals

While several mechanisms can be imagined by which an external electric field can affect electronic excitation energy transfer in crystals, the simplest possibility involves changing the energy level spacings of neighboring molecules. Energy transfer from one molecule to another is affected by an energy mismatch or loss of resonance. In a band model, presumably valid at low temperatures, this loss of resonance decreases the exciton bandwidth and reduces the exciton group velocity. When the bandwidth is comparable to the inhomogeneous broadening, an abrupt decrease in the rate of energy transfer can be expected, reflecting the phenomenon of Anderson localization. At higher temperatures, the energy mismatch can be accommodated by phonon emission and absorption processes. The dependence of the energy transfer rate constant on electric field and temperature for the case of coherent energy transfer and for the limit of incoherent energy transfer is predicted for a simple model system.     

Deformation-induced After-Glow in [(C2H5)4N]2MnBr4 Crystals

The mechanoluminescence appears in [(C₂H₅)₄N]₂MnBr₄ crystals even after their mechanical deformation. During the excitation of mechanoluminescence by the impact of a piston on to the crystals, the peak corresponding to the mechanoluminescence intensity versus time curve and the total intensity of mechanoluminescence increase with the impact velocity and decrease with the temperature of the crystals. It seems that the electric field produced during the inpact of the piston on to the crystal may perturb the ground and excited states of the molecules comprising the crystals. Thus the mechanoluminescence may follow the rate of compression during the deformation of the crystal and it may decay with the decay rate of phosphorescence after the compression. The mechanoluminescence and high pressure photoluminescence spectra are also reported.