GeO2含量对掺铒锗碲酸盐玻璃物性和光谱特性的影响

本文研究了x GeO2-(70-x)TeO2-5K2O-5Na2O-10Nb2O5-10ZnO-0.2Er2O3(x=0,10,25,50,70(摩尔百分数))玻璃的物性和光谱特性,讨论GeO2含量对锗碲酸盐玻璃物性和光谱特性的影响.研究发现:GeO2的加入提高了碲酸盐玻璃热稳定性,并且使玻璃的最大声子能量略微增加;随GeO2的增加,掺Er3+锗碲酸盐玻璃的Judd-Ofelt强度参量Ω2和Ω6逐渐增大,但玻璃受激发射截面有减小的趋势;由McCumber理论,计算了掺铒锗碲酸盐玻璃在1.53μm处最大受激发射截面为9.92×10-21cm2,Er3+离子4I13//2→4I15/2发射谱的最大荧光半高宽为52nm,同时,实验发现,在977nm LD抽运下,掺铒锗碲酸盐玻璃存在较强的荧光上转换现象,随GeO2含量的增加,上转换荧光强度呈降低的趋势.     

MgO-TiO2二元系熔体结构的原位超高温拉曼光谱研究

利用激光加热超高温气动悬浮熔体和皮秒拉曼光谱测试技术耦合,有效抑制超高温黑体辐射对拉曼光谱的影响,获得了高信噪比的二元镁钛酸盐系列熔体拉曼光谱。定量分析了熔体中团簇结构的分布及其随组分浓度的变化规律。定量分析表明：MgO-TiO₂二元系熔体中存在H₀、Q₀、Q₁、Q₂和Q₃微结构单元,且随TiO₂浓度的增加,熔体中四配位TiO₄四面体逐渐向六配位TiO₆八面体转变。     

三硼酸铋晶体及其高温熔体结构的拉曼光谱研究

测量了BiB3O6晶体从常温到熔融态的拉曼光谱,考察了其温致结构变化和预测了熔体的结构基元。同时,采用量子化学从头计算和密度泛函理论对拉曼光谱进行了计算和结构分析。结果表明,随着温度的升高,对包含阳离子Bi的外部晶格和[BO3]3-硼氧三角形基团结构的温致结构影响有限,却有效地削弱了[BO4]5-硼氧四面体基团结构,其松弛度增加,稳定性变差,并在熔体结构中彻底消失。研究表明BiB3O6熔体主要以硼氧六元环[B6O12]6-的形式存在,阳离子Bi起电荷平衡作用,其氧配位数为3,有别于晶体中的6。     

NaF-AlF_3二元系熔盐固相晶体与熔体结构的拉曼光谱及其计算模拟研究

采用量子化学密度泛函计算方法对NaF-AlF3系熔盐的若干典型固相晶体结构进行了计算模拟拉曼光谱研究,并对光谱的振动形式进行了归属,发现特征峰位与铝配位数关系明显;同时,对NaF-AlF3二元系熔盐固相晶体及熔体结构进行了原位变温拉曼光谱实验研究。结果表明,基于计算模拟的振动谱峰归属分析,为NaF-AlF3系熔盐的微结构识别和温致结构变化提供了解析依据,而且随着AlF3浓度的增加,熔盐中铝六配位结构逐渐转化为铝四配位结构。     

二元钠硅酸盐玻璃及其熔体微结构的高温拉曼光谱及核磁共振研究

本文采用拉曼光谱研究不同配比的二元钠硅酸盐玻璃,结果显示碱金属阳离子的浓度影响结构中桥氧的含量,且不同初级结构Qi具有不同的特征峰。对Na2O·3SiO2玻璃进行高温拉曼和核磁共振研究,分别采用精细结构Qjklmi(m1h,m2q,m3t)和Qjklmi取代初级结构Qi进行解谱拟合和结构分析得到得到初级微结构单元的实际分布,结合量化分析结果计算其拉曼散射截面,定量分析Na2O·3SiO2玻璃及熔体在升温状态下结构随温度的变化。从室温到到熔态,Qi结构之间存在动态平衡,Na2O·3SiO2玻璃随着温度的升高从玻璃态到高弹态,最后经历粘流态到熔态。     

Li_2B_4O_7晶体、玻璃及其熔态结构的高温Raman光谱研究

采用半导体脉冲激光光源和时间分辨探测技术 ,测定了二硼酸锂 (Li2 B4O7)晶体、玻璃及其熔融态的常温及高温拉曼光谱 (在 2 98～ 1 773K的温度范围 ) ,观察了其在高温下的相转变、升温过程及其熔体的特征光谱变化。通过谱图解析 ,研究分析了熔体微结构单元的分布和转化及其与固态晶体和玻璃态的区别     

SiO2/Ge:SiO2/SiO2夹层结构红外光发射的起源

我们借助傅立叶变换红外光谱（FT－IR）以及光致激发谱（PLE）,研究SiO2/Ge:SiO2/SiO2夹层结构红外光发射的起源。谱分析表明,该红外光发射并非起源于纳米锗、硅的量子限制效应以及锗、硅的中性氧空位,而与锗的氧化物紧密相关。PLE的结果证实它们来源于GeO色心TⅡ‘→S0的光学跃迁,给出的GeO电子态模型描述了载流子激发和复合的过程。     

CaSiO_3及其熔体结构的高温拉曼光谱研究

采用铜蒸气脉冲激光光源和时间分辨探测技术,测定了CaSiO3晶体及其熔融态的常温及高温拉曼光谱(在298～2000K的温度范围),观察了其在高温下的相转变、升温过程及其熔体的特征光谱变化。通过谱图解析,研究分析了熔体微结构单元硅氧四面体Qn(n为单个硅氧四面体的桥氧数)分布、聚合状况及其与固态晶体的区别     

退火处理对W:Bi4Ge3O12和Bi12GeO20晶体发光性能的影响

通过提拉法制备了W:Bi4 Ge3 O12和Bi12GeO20晶体,测试了晶体的吸收光谱、光致发光谱和发光衰减时间等.W:Bi4 Ge3 O12的可见光发光强度比纯Bi4 Ge3 O12有所增强,而且N2中退火处理对W:Bi4Ge3O12发光有进一步增强作用.Bi12GeO20在N2中退火处理后在745 nm附近有发光...     

二甲基亚锗基锗烯与乙醛生成螺锗杂环化合物反应机理的密度泛函理论研究

用B3LYP/6-31G*方法研究了单重态二甲基亚锗基锗烯(Me₂Ge=Ge:)与乙醛环加成反应的反应机理,根据该反应的势能面可以预言,该反应有一条主反应通道. 该反应所呈现的反应规律为：两反应物通过[2+2]环加成反应首先生成了一锗杂四元环锗烯,由于该锗杂四元环锗烯中Ge:原子的4p空轨道与乙醛的?轨道形成了π→p授受键,从而使锗杂四元环锗烯进一步与乙醛结合生成了一中间体. 由于该中间体中的Ge:原子在过渡态之后发生了sp³杂化,从而使该中间体经过渡态异构化为了一螺锗杂环化合物. 该研究结果从理论上揭示了单重态二甲基亚锗基锗烯(Me₂Ge=Ge:)与乙醛环加成反应的反应机制,奠定了亚锗基锗烯(H₂Ge=Ge:)及其衍生物(X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar?)与非对称性π键化合物环加成反应的理论基础.     

锗酸盐晶体压致非晶化的研究

高压拉曼散射研究表明．ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７三种晶体分别在７，１２和１１ＧＰａ压力下转变为非晶。在高于起始转变压力以上一定范围压致非晶是可逆的，ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７压致非晶的不可逆转变压力分别为１４．１，２０和２０ＧＰａ。压致非晶ＣｕＧｅＯ３的重新晶化温度在６００℃附近。锗酸及系列晶体的压致非晶化与它们的成份和结构有关，随着在这一系列晶体中Ｌｉ２Ｏ含量的增加，压致非晶化的压力趋于减小。     

Pressure-induced sharp coordination change in liquid germanate

Local structures around germanium in liquid germanate have been investigated by means of in situ x-ray absorption measurements up to 9 GPa at 1273 K. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated germanium becomes stable. The GeO6 octahedron in the high-density liquid is more compressible than that in solids.     

Influence of strain distribution on the morphology evolution of a Ge/GeO_2 core/shell nanoparticle confined in ultrathin Al_2O_3 thin film by surface oxidation

The influence of strain distribution on morphology evolution of Ge/GeO2 core/shell nanoparticle confined in ultrathin Al2O3 thin film by surface oxidation is investigated. A finite-element simulation is performed to simulate the morphology evolution of the confined Ge/GeO2 core/shell nanoparticle under the influence of the local strain distribution. It indicates that the resultant oxidation-related morphology of Ge/GeO2 core/shell nanoparticle confined in ultrathin film is strongly dependent on the local strain distribution. On the other hand, the strain gradients applied on the confined GeO2 shell can be modified by the formation of polycrystalline GeO2 shell, which has potential application in tailoring the microstructure and morphology evolution of the Ge/GeO2 core/shell nanoparticle.     

Na-doped optical Germanium bulk crystals

In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 10¹⁵ cm^?3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5?10¹³ to 4?10¹⁴ cm^?3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.     

New opportunities for high-resolution solid-state NMR spectroscopy of oxide materials at 21.1- and 18.8-T fields

We present here high-resolution solid state NMR spectra of several oxide and silicate materials that illustrate the improvements obtainable with very high external fields (18.8 and 21.1 T), with probes capable of tuning to a wide frequency range that allow observations of nuclides from high to low magnetogyric ratio. We discuss 27Al MAS spectra for the zeolite scolecite (CaAl2Si3O10 x 3H2O), 17O MAS data for analcime (NaAlSi2O6 x H2O), calcium monoaluminate (CaAI2O4), and titanite (CaTiSiO5), 39K spin-echo spectra for leucite (KAlSi2O6), microline (KAlSiO8), muscovite (KAl2(AlSi3O10)(OH2) and a potassium aluminosolicate glass, and preliminary 73Ge spin-echo MAS spectra for crystalline and glassy germanium dioxide (GeO2).     

在硅酸盐矿物,玻璃和熔体中Si和Al的配位与局部结构：K—边 …

本文采用步辐射的ＳｉＫ－边Ｘ－射线吸收近边结构（ＸＡＮＥＳ）谱研究了Ｓｉ在ＳｉＯ２－Ｐ２Ｏ５和Ｎａ２Ｏ－ＳｉＯ２－Ｐ２Ｏ５的低压磷硅酸盐玻璃中结构与配位,以及Ｓｉ的配位几何随玻璃中Ｐ２Ｏ５含量而变化：同步辐射的Ａｌ Ｋ－边ＸＡＮＥＳ谱研究了Ａｌ在铝硅酸盐成分为ＮａＡｌＳｉ２Ｏ６－ＮａＡｌＳｉ３Ｏ８的玻璃和熔体中的配位和局部结构,并提供了直接的实验证据该成分的玻璃体系中由于压力的变化所诱导Ａｌ配位的     

锗酸锌锰荧光体发光学与荧光瞬态衰减研究

制备一系列锗酸锌锰荧光体,并探讨其发光特性、瞬态荧光衰减与色度值与所掺杂锰离子含量之间的相互关系.本系列荧光体锰离子发射峰波长,随Mn²⁺含量由0增加0.05,由527nm红移至534nm.实验表明这可能与Mn²⁺所占据的四面体格位,遭扭曲而导致晶场强度变弱有关.本系列荧光体的CIE色度坐标值,则随所掺杂Mn²⁺含量,仅有微小改变.锗酸锌锰荧光体瞬态荧光衰减的研究结果表明:锗酸锌基质的衰减生命期在纳秒范围;随Mn²⁺掺杂量增加,在毫秒范围的锰离子荧光衰减生命期逐渐缩短.此现象可能与Mn²⁺-Mn²⁺离子对中,Mn²⁺的自旋交换相互作用有密切关系.     

Influence of the deposition and annealing temperatures on the luminescence of germanium nanocrystals formed in GeO x films and multilayer Ge/SiO2 structures

Physics of the Solid State - The GeO x films and multilayer nanoperiodic Ge/SiO2 structures containing germanium nanocrystals were prepared by physical vapor deposition in vacuum. The properties of...     

IR absorption and Raman spectra of single crystals of stable germanium isotopes

The Raman and IR absorption spectra of single crystals of germanium isotopes ⁷²Ge, ⁷³Ge, ⁷⁴Ge, and ⁷⁶Ge in the region of phonon absorption and interband electronic transitions are studied at room temperature. The dependence of the Raman peak position on the atomic mass has the form ν ~ M^–1/2. The shifts of the phonon absorption peaks of individual isotopes with respect to germanium of natural isotopic composition ^natGe are determined. With increasing average atomic mass of germanium, these peaks shift to longer wavelengths. In the region of interband electronic transitions, the intrinsic absorption edge of ⁷⁶Ge is observed to shift by 1 meV to higher energies with respect to Ge of natural isotopic composition. For isotopes with atomic masses close to that of natural germanium (⁷²Ge,⁷³Ge, ⁷⁴Ge), we found no significant difference in the band gap width at room temperature.     

Stability of valence alternation pairs across the substoichiometric region at Ge/GeO2 interfaces

Through hybrid density functional calculations, we compare the Ge–Ge bond energy with the formation energy of a valence alternation pair as the O concentration varies across the Ge/GeO₂ interface. First, hole trapping energies are calculated for three atomistic models with different O concentrations: bulk Ge with isolated O atoms, amorphous GeO, and amorphous GeO₂ with an O vacancy. The reaction is then broken down in three steps involving the breaking of a Ge–Ge bond, charge transfer processes involving dangling bonds, and the formation of a threefold coordinated O atom. The energy of each elemental reaction is estimated through suitable model calculations. The charge transition levels resulting from this analysis agree with those obtained for the atomistic models. Our estimates indicate that hole trapping at low O concentrations occurs at no energy cost for p-type germanium owing to the formation of threefold-coordinated O atoms. Applied to n-type Ge, our analysis indicates that electron trapping in dangling bonds obtained from the breaking of Ge–Ge bonds is unfavorable. The formation energy of a valence alternation pair is evaluated and discussed in relation to previous results.