Y1-xPrxBa2Cu3O7+δ的红外反射谱

测量了温度范围为4.2—300K的Y_1-xPr_xBa₂Cu₃O_7+δ(x=0,0.1,0.2,0.4,0.5,0.61.0)的红外反射谱,发现在低温下Ba模有双模行为,随着x值增大双模强度反转,在YBa₂Cu₃O_7+δ中已被判定为Y模的位于194cm^-1的反射峰的位置与Pr的含量无关,即用Pr部份或全部替代Y时此峰不发生频移。建议Pr在Y_1-xPr_xBa₂Cu₃O_7+δ,中是正4价,Pr的替代使原来可移动的空穴被定域在Pr的周围,使超导电性受到压制。 关键词：     

LaBa2Cu3-xCoxOy体系中声子振动和自旋关联的研究

我们用X射线衍射,红外光谱以及电子顺磁共振等实验手段,对LaBa2Cu3-xCoxOy (0≤x≤1.0)系列样品进行了研究.研究表明:所有样品皆为单相正交结构.对于不掺杂的样品在535cm-1和585cm-1附近有两个显著的吸收峰,分别相应于Cu(1)-O(1) 和Cu(2)-O(2) 的伸缩振动.在低掺杂区(0≤x≤0.5)535cm-1处的红外峰随x增加向低频方向移动,而585cm-1处的红外峰位置基本不变.当x＞0.5时,这两个峰逐渐宽化,最后变成单个宽峰(x=1.0).掺杂样品在657cm-1处的声子振动模随掺杂量增加向高频方向移动,该峰为Cu(1)-O(4)的伸缩振动模.本文分析了晶体结构和声子振动以及自旋关联变化的相互关系.     

孤子振动模的定域性

对于聚乙炔中孤子的五个定域振动模,本文研究了它们的位形随链长的变化而演变的情况,从而可确定其定域性。本文同时考察了开链和闭环两种情况。对于闭链,五个定域模定域于孤子附近,其形状与链长无关。对于开链,定域模g₁,g₂,g₃和g₅的位形不随链长而改变,因而是完全定域的,但是g₄的两翼随链长增加而变宽,定域性不完全。 关键词：     

掺杂聚乙炔中的孤子振动定域模

在SSH模型基础上,本文研究了掺杂聚乙炔链中杂质势对孤子振动模的束缚影响。不同边界条件下的数值计算发现Goldstone模将受到杂质钉扎并出现两个新的定域模g₁′和g₂′。另外,还得到了其它已知的定域模g₂,g₃和g₅,这些定域模随杂质势的敏感程度各有不同,在所取参数下取得了与实验基本一致的结果。 关键词：     

半导体中定域模,准定域模晶格振动的光谱研究

本文讨论了用光学方法研究杂质诱发定域化振动模的理论模型,分门别类地论述了半导体中杂质诱发的定域模、禁带模、共振模和准定域模晶格振动及非晶态半导体的晶格振动谱,给出了它们的综合结果。半导体中杂质诱发定域模已被人们广为研究,作者主要以自己的结果阐述了禁带模、共振模、准定域模和非晶态半导体振动谱研究在近年来取得的重要进展。除以较多篇幅研究各种定域化振动模的位置外,本文还从键—电荷模型出发讨论了杂质诱发振动吸收带的强度。     

红色荧光粉NazCa1-x-2y-zBiyMoO4∶Eu3+x+y发光研究

采用高温固相法制备系列红色荧光粉Naz Ca1-x-2y-zBiyMoO4 ∶ Eu3+x+y (y,z=0,x=0.24,0.26,0.30,0.34,0.38; x=0.30,y=0.01,0.02,0.03,0.04,0.05,0.06,0.07,z=0; x=0.30,y=0.04,z=0.38).用X射线粉末衍射(XRD)法测试了所制样品晶相结构.采用荧光光谱仪对样品的发光性能进行了表征,结果表明:当Eu3+单掺杂量浓度x=0.30时,荧光粉(Ca0.70 MoO4∶Eu3+0.30)的发光强度最强;当Eu3+-Bi3+共掺杂量浓度y=0.03时,电荷迁移带(CTB)强度达到最强,而对于Eu3+特征发射峰,当共掺杂浓度y＜0.03时,位于393 nm处的激发峰强度比464 nm强,共掺浓度y＞0.03时,464 nm峰比393 nm峰强,共掺浓度为y=0.04时,393和464 nm处两峰位置强度都达到最强.作为电荷补尝剂的Na2 CO3掺入上述荧光粉中后,荧光粉激发和发射强度明显地增强.结果表明,通过调节Bi3+ /Eu3+掺杂比例可以改变位于近紫外光393 nm和蓝光区464 nm处激发光相对强度.     

半导体中定域模,准定域模晶格振动的光谱研究

本文讨论了用光学方法研究杂质诱发定域化振动模的理论模型,分门别类地论述了半导体中杂质诱发的定域模、禁带模、共振模和准定域模晶格振动及非晶态半导体的晶格振动谱,给出了它们的综合结果。半导体中杂质诱发定域模已被人们广为研究,作者主要以自己的结果阐述了禁带模、共振模、准定域模和非晶态半导体振动谱研究在近年来取得的重要进展。除以较多篇幅研究各种定域化振动模的位置外,本文还从键—电荷模型出发讨论了杂质诱发振动吸收带的强度。     

非晶态快离子导体(AgI)x(Ag4P2O7)1-x的声学性质

用液氮骤冷方法制备了(AgI)_x(Ag₄P₂O₇)_1-x系列非晶态快离子导体。对AgI摩尔浓度x=0.50,0.60,0.67,0.75,0.80的样品,在77—300K温度范围及2,5,10,15MHz的频率上测量了纵波和横波的超声衰减和声速。发现在200—240K附近存在一个异常强的弛豫型超声吸收峰,随AgI含量的增加,该峰的位置向低温方向移动,且峰的高度增大。在实验的温度范围内,观察到纵波和 关键词：     

掺C的MgB2块材在静态Ar气氛下成相的研究

我们制备了掺碳二硼化镁系列样品MgB2-xCx(x=0、0.02、0.05、0.1、0.13、0.15、0.17),得到了x=0.02、0.05、0.13、0.15、0.17等样品在高温烧结过程的升温阶段的R～T曲线(简称为HT R～T曲线).发现这些样品的成相温度比不掺碳的MgB2样品的成相温度要低一些,处于500℃附近.我们也对x=0.0、0.05、0.1、0.13、0.15、0.17这一系列样品的X光图谱,低温M～T曲线,R～T曲线进行了测量和讨论.     

钒掺杂La1.85Sr0.15Cu1-xVxO4＋δ超导体系的结构研究

本文讨论了钒掺杂La1.85Sr0.15Cu1-xVxO4 δ体系的结构.与以往二三价元素掺杂不同,V掺杂的最高掺杂浓度较大,为0.15.精修结果表明,样品中V为 4价,并且全部替代了Cu.晶胞参数a,b随掺杂量x的增加而增加,c随x的增加减小.x=0.10时发生四方-正交相变.随掺杂含量的增加样品结构的变化在红外吸收谱中也有对应.随V含量的增加,500cm-1处的吸收峰的强度和位置都没有变化,这表明V替代在了Cu位.对于350cm-1处的吸收峰,x=0.5时在其附近左侧327cm-1处出现一个吸收峰,当x=0.10时在其右侧400cm-1处又出现一个吸收峰.400cm-1处吸收峰的出现是和四方-正交相变(x=0.10时发生四方-正交相变)相对应的.     

Ab initio studies on the mechanic and magnetic properties of PdHx

Based on ab initio total energy calculations,the structural,electronic,mechanic,and magnetic properties of PdH x are investigated.It is found that bulk modulus of PdH x is larger than the metal Pd with the hydrogen storage except Pd 4 H 2.The calculated results for the magnetic moments show that the hydrogen addition weakens the magnetic properties of the PdH x systems.A strong magneto-volume effect is found in PdH x structures as well as Pd.The transition from paramagnetism to ferromagnetism is discussed.The corresponding densities of states for both structures are also shown to understand the magnetic behaviour.     

Investigation of the “50 K-transition” in PdH0.73 by γ-ray and neutron diffraction

Rocking curves of the (111)-reflection in a PdH_0.73 single crystal have been measured with 412 keV γ-rays during an ageing experiment at 50 K up to 260 h. The width (variance) shows an overall increase of 1.5% ± 0.3% and the integrated intensity a maximum at 100 h.An investigation at superstructure points in the same PdH_0.73 crystal was made using neutron scattering. An enhancement of the elastic diffuse scattering has been found at the $\text{(1}\text{1}\text{2}\text{0)}$ and (110)-positions after an ageing at 54 K up to 300 h. The intensity ratio to the fundamental (002)-reflection is 10^-4. It is concluded that below the anomaly temperature a local ordering of the hydrogen atoms occurs and the growth of the ordered zones slows down after 100 h ageing.     

Hydrogen mobility in crystalline and amorphous Zr2PdHx

NMR measurements of proton rotating-frame relaxation times were made to deduce hydrogen diffusion parameters for crystalline and amorphous Zr₂PdH_x. Enhanced proton mobility was observed in glassy a-Zr₂PdH_2.9 relative to diffusion behavior in any crystalline Zr₂PdH_x sample. Both host crystal structure and proton site occupancy make significant contributions to the diffusion process where smaller activation energies correspond to jumps involving octahedral sites.     

氢化锆(ZrH1.7)和钯氢(PdH0.7)光学声子的温度效应

在本院重水堆旁的铍过滤探测器中子非弹性散射谱仪上,对氢化锆(ZrH_1.7)(含碳0.2％)和钯氢(PdH_0.7)两种金属氢化物在室温和低温(97K)两种温度下,分别测定了光学声子能谱。结果表明:氢化锆的光学声子能级是等间距的,能级宽度基本上不随温度变化,即光学声子的非谐性是微弱的,较好地遵从爱因斯坦的谐振模型;而钯氢的第二个光学声子能级间距大于第一个能级间距约8meV,并且光学声子能级的宽度从室温下的38meV变化到低温(97K)下的20meV,这表明对钯氢的超导性起决定作用的光学声子,存在较明显的非谐性。 关键词：     

Model of instabilities in PdHx and PdDx

The instability and inhomogeneity of the PdH_x and PdD_x systems is discussed. A simple model based on the existence of more than one local electronic and or ionic configuration is proposed, and the results of this model are shown to be consistent with several important lattice properties of these systems including a difference between the Pd-H and Pd-D force constants.     

Electronic states and Fermi surface properties of α-phase PdHx

Calculations based on a muffin tin model for the electronic structure of the random interstitial alloy PdH_x are presented together with the first high resolution de Haas-van Alphen data for this system in the α-phase. In the dilute limit good agreement is obtained for the concentration dependence of the areas of several extremal orbits. The behavior of the PdH_x Fermi surface is unique in that the Γ-centered electron orbits are found to grow at approximately the rate predicted by the rigid band model while the X-centered hole pockets shrink at only half the rigid band rate.     

Magnetic characterization of a hydrogen phase trapped inside deep dislocation cores in a hydrogen-cycled PdH x (x ≈ 4.5 × 10−4) single crystal

The magnetic characterization of Pd single crystals deformed by cycling in a hydrogen atmosphere has been performed. Based on evidence obtained from thermal desorption analysis, it is shown that the condensed hydrogen phase formed inside deep dislocation cores in PdH _x (x = H/Pd ≈ 4.5 × 10⁻⁴) is tightly bound with a Pd matrix. The activation energy of hydrogen desorption from these cores was found to be as high as e = 1.6eV/H-atom, suggesting the occurrence of a strong band overlapping between Pd and H atoms. SQUID measurements carried out in a weak magnetic field (H < 5.0 Oe) showed an anomalous diamagnetic contribution to the DC and AC magnetic susceptibilities of the PdH _x sample at T < 30 K resulting in the presence of the hydrogen phase. It is suggested that the anomalous diamagnetic response in PdH _x is caused by the presence of a hydrogen dominant phase, tightly bound with a Pd matrix inside the dislocation cores (nanotubes). The text was submitted by the authors in English.     

Role of hydrogen in the absorption of ionizing radiation energy by a metal-hydrogen system

Ab initio calculations of the electronic structure of pure Pd, pure Ti, and PdH_x and TiH_x (x = 1, 2, 3) systems are performed within the local density approximation. It is found that the electronic subsystem of metals containing dissolved hydrogen increases their capacity to absorb the energy of electromagnetic radiation and accumulate it for a longer time than pure metals. These two factors promote the nonequilibrium migration of hydrogen atoms and their release from metals upon exposure to ionizing radiation.     

Comparison between the magnetic susceptibilities of Pd1−xAgx and single phase PdHn

The rapid decrease of the isothermal magnetic susceptibility χ of single phase PdH_n with n ( = atomic ratio H/Pd) above the critical temperature T_c = 564 differs from that of the magnetically similar single phase system Pd_1−xAg_x (x: silver mole fraction) at the same temperature and at equal valence electron concentrations (n = x), i.e. χ (PdH_n)−χ(Pd_1−xAg_x) <0. By use of a semiphenomenological susceptibility ansatz related to the nonideal solution behaviour of H (Ag) in Pd the susceptibility difference is interpreted as an electronic excess effect.The analysis of the steep descent of the magnetic susceptibility also applies to the Pd-rich side of PdH_n in the subcritical temperature region (so-called α-phase) and can be supported by ¹⁰⁵Pd Knight shift data at 348 K.     

Tunneling observation of the superconducting energy gap in the palladium hydride thin films

Superconductivity in hydrogen charged palladium thin films has been studied. Using niobium based tunneling junctions the energy gap in PdH_x samples, with different values of x and hence of T_c have been observed.