共查询到18条相似文献,搜索用时 328 毫秒
1.
2.
3.
用坩埚下降法(Bridgman)生长出了Bi离子掺杂的CdWO4单晶.测定了晶体不同部位的吸收光谱、发射光谱和X射线电子能谱(XPS).Bi离子的掺入引起CdWO4晶体的吸收边从345 nm红移到399 nm.在311 nm, 373 nm,808 nm和980 nm光的激发下,分别观测到中心波长为470 nm,528 nm,1078 nm和较弱的1504 nm四个不同发射带.Bi:CdWO4单晶的XPS谱分别与Bi2
关键词:
Bi离子
荧光光谱
X射线电子能谱
4单晶')" href="#">CdWO4单晶 相似文献
4.
通过对少量Zn掺杂Bi2212单晶样品不同温度下的磁滞回线的测量,根据Bean临界态模型得到了样品在不同温度和磁场下的临界电流密度.发现不同温度下的临界电流密度与磁场的关系可以用Jc(H,T)=Jc(0,T)exp(-Hα)进行拟合,并且拟合参量α随温度的上升而增大,而在Pb掺杂和纯Bi2212单晶中α值基本上是不随温度变化的.将得到的Jc与Pb掺杂和纯Bi2212单晶的结果进行比较,发现在相同的温度和磁场下Zn掺杂样品具有最高的临界电流密度,表明少量Zn掺杂使得样品的临界电流密度得到提高.Zn掺杂对Bi2212体系临界电流密度的提高主要来源于在材料中引入了有效的涡旋钉扎中心,而Pb掺杂体系中Jc的提高是体系的层间耦合增强导致的结果. 相似文献
5.
传统固相反应所合成的锶系钌铜氧化物,通常总伴有少量铁磁性SrRuO3杂相.采 用氧(或空 气)_水蒸气混合气氛下的新型固相反应,既能成功合成锶系钌铜氧化物的前驱物纯相Sr2G dRuO6(211相), 也能进一步在相对低的温度下成功合成锶系钌铜氧1222纯相化 合物RuSr2(Gd,Ce)2Cu2O10 (Ru_1222), 使其中SrRuO
关键词:
水蒸气参与的新型固相反应
2(Gd')" href="#">RuSr2(Gd
2Cu2< /sub>O10纯相')" href="#">Ce)2Cu2< /sub>O10纯相
3杂相')" href="#">SrRuO3杂相
电学性质 相似文献
6.
用化学动力学探讨了Bi系超导相形成的机理,提出反应活化能是控制超导相形成的关键因素。在纯Bi系2223名义成份下,2212相的形成满足“晶核形成生长”自催化动力学模型,其动力学方程为α_(2212)=1—exp(—k_(2212)t~(2.5))。2223相的形成较好地符合“收缩晶核界面”反应模型,动力学方程为1—(1—α_(2223))~(1/3)=k_(2223)t。以0.35molPb替代Bi后,2212相形成的动力学规律没有本质改变,但是2223相的形成表现出区域反应的自催化效应,其相应的动力学方
关键词: 相似文献
7.
系统地研究了Gd掺杂对Bi2Sr2Ca1-xGdxCu2Oy单晶超导电性及各向异性电阻率的影响.Tc满足Tc/Tc,max=1-82.6(ax+b)2,并随Gd含量的增加而下降,这是由于Gd掺杂引起载流子浓度减小所导致.在x≥0.19时,ρab(T)在Tc附近有类半导体行为,dρab/dT随Gd含量增大而增大.ρc(T)呈半导体行为,并可用唯象公式ρc(T)=(a/T)exp(Δ/T)+bT+c加以描述.电阻率各向异性ρc/ρab随掺杂浓度增大而增大. 相似文献
8.
9.
10.
铋(Bi)和铅(Pb)都是重元素,有很强的自旋-轨道耦合作用,由于原子半径接近,可形成丰富的原子取代合金结构.尽管对高温合金相有了较深入的研究,但对其低温物相的结构和超导物性的认识还很不全面.本文采用低温共沉积和低温退火的方法,在Si(111)-(7×7)衬底上制备了一种基于Bi(110)单晶结构中部分Bi原子被Pb取代的铅铋合金低温相超薄膜新结构,利用扫描隧道显微术(STM)对其结构和电子学性质进行了表征.通过结构表征,确定了合金薄膜表面呈现21/2×21/2R45°重构的PbBi3合金相,其母体Bi(110)结构中25%的Bi原子被Pb取代了.通过STM谱学测量,发现合金相PbBi3为超导相.变温实验表明, PbBi3相的超导转变温度为6.13 K.在外加垂直磁场下出现的磁通涡旋结构表明PbBi3薄膜是第Ⅱ类超导体,估算出上临界磁场的下限为0.92 T.测量了由Bi(110)-PbBi3组成的共面型和台阶型正常金属-超导体异质结中... 相似文献
11.
Liyun Zhong Jiye Cai Yi Liu Honggao Tang Yuping Sun Jiaju Du 《International Journal of Infrared and Millimeter Waves》1991,12(3):239-249
In this paper we study the room-temperature infrared transmission spectra (400–1600cm–1) and far-infrared diffuse reflection spectra (50–450cm–1) in Pb-doped Bi–Sr–Ca–Cu–O (2223) single phase (Tc=107k, sp1), multiphase (Tc=110k, sp2) and nonsuperconducting samples (sp3). The spectral features in superconductor are totally different from those in nonsuperconductor, which show the different crystal structure. The correlation existing between a factor group analysis of the phonons in (2223) and (2212) compounds affords a tentative assignment of ir-active modes in Pb-doped (2223) single phase by comparison with reported data in (2212) materials. The Cu–O stretching Eu vibration (605cm–1) of CuO2 layers is the characteristic vibrational mode related perovskitelike crystal structures. Two phonon coupling effect emerges in the infrared transmission spectra in Pb-doped superconductor. The Ca–O vibration A2u (254cm–1) might be related to superconductivity of Bi-based family. 相似文献
12.
Nanlin Wang Qirui Zhang Yugui Wang Mingrong Ji Xianming Liu 《Zeitschrift für Physik B Condensed Matter》1992,86(3):325-328
The electronic structure of Bi-based 2223 single phase superconductor has been studied by ultraviolet and X-ray photoemission. By comparison with that of 2212 phase superconductor, we find a higher density of states nearE
F
for 2223 phase. From analysis of the Cu 2p core-level spectroscopy, we obtain a relatively smaller charge transfer energy between copper and oxygen as well as the Coulomb repulsion energy on Cu site for 2223 phase. We relate these changes to the increase of hole concentration from 2212 to 2223 phase. The experimental results support the viewpoint that the transition temperature should be correlated with the density of states atE
F
. 相似文献
13.
Bingsen Zhang 《Applied Surface Science》2011,257(22):9377-9381
Bi2Sr2CaCu2O8+δ (Bi2212) thin film is an important superconducting material ascribed to its high transition temperatures and low toxicity, but the application of Bi2212 thin films is limited due to the appearances of intergrowth and impurity phases. To achieve high-quality Bi2212 thin film by molecular beam epitaxy (MBE), the oxidizing gas pressure and substrate temperature are the key parameters. Here, the phase formation in Bi-based thin films grown by MBE was studied as a function of oxidizing gas pressure and substrate temperature. Furthermore, the thermodynamic parameters have been investigated through enthalpy change. This study indicates that the substrate temperature was increased with the enhancing of ozone partial pressure when the composition ratio is fixed, Bi2212 single phase can be formed. Moreover, the chemical stability decreases in the order of Bi2Sr2CuO6+δ > Bi2212 > Bi2Sr2Ca2Cu3O10+δ. 相似文献
14.
By making a combination of both point contact and barrier type tunnel junctions on a single sample of the highT
c superconductor BSCCO (2212) single crystal, we have shown that as the tunneling tip is slowly retracted from the surface
a point contact junction gradually evolves from a N-S short to a high resistance tunnel junction. The scaled dynamic conductance
(dI/dV) of this point contact tunnel junction becomes almost identical to that of a conventional barrier type tunnel junction and
both show a linear dI/dV —V curve. The observation implies that at high resistance a point contact junction behaves in the same way as a barrier type
tunnel junction. We suggested that the almost linear tunneling conductance obtained in both the cases most likely arises due
to an intrinsic characteristic of the surface of the crystal comprising of a mosaic of superconducting regions of the order
of a few nanometers. We also conclude that the barrierless (N-S) point contact obtained by piercing the surface oxide layer
of the crystal shows Andreev reflection which we suggest as the origin of the zero bias anomaly often observed in point contact
junctions. 相似文献
15.
Amagoia Aguirrechu-Comerón Plácida Rodríguez-Hernández Ulises R. Rodríguez-Mendoza Oriol Vallcorba Alfonso Muñoz Sandrine Perruchas 《高压研究》2019,39(1):69-80
Combined high pressure single crystal X-ray diffraction experiments and ab initio simulations based on the density functional theory have been performed on a copper(I) iodide cluster formulated [Cu4I4{PPh2(CH2CH?=?CH2)}4] under high pressure up to 5?GPa. An exhaustive study of compressibility has been done by means of determination of isothermal equations of state and structural changes with pressure at 298?K taking advantage of the single crystal is more precise than powder X-ray diffraction for this type of experiments. It allows us to report the evidence of the existence of an isostructural phase transition of second order at 2.3?GPa not detected so far. 相似文献
16.
N.B. Chanh Y. Haget A. Meresse D. Louer R. Shirley 《Journal of Physics and Chemistry of Solids》1981,42(3):217-225
The polymorphism of 2-bromonaphthalene has been studied by both crystallographic and energetical methods. Three crystalline forms have been characterized, respectively denoted BrIII, BrII and BrI. The first one is the stable form up to 319 K. At this temperature a first order phase transition occurs which breaks the single crystal and leads to a disordered structure BrI isotypic with the naphthalene one. The BrII form is a metastable one which appears when cooling the BrI, form; when so formed, the BrII phase can give again the BrI one by annealing; so that the BrI-BrII transition is reversible. This second order transition extends over a large temperature range (275–319 K), it does not destroy the single crystal and corresponds to a substructural modification along the c axis of the monoclinic cell. The anomalies of the Cp curve and the variations of the principal components of the thermal expansion tensor suggest that there are two competitive temperature dependent molecular reorientations. The transition BrII→BrIII which leads to the stable ordered form is spontaneous at room temperature, it takes place sluggishly and destroys the single crystal.Cell parameters of the BrIII form have been determined from powder data using an automatic indexing method: a = 9.578(1) Å, B = 9.601(1) Å, c = 10.303(1) Å, α = 100.79(1)°, β = 109.06(1)°, γ = 101.77(1)°. (Figure of merit M20 = 86.) 相似文献
17.
H. Grawe H. H. Bertschat R. Kowallik S. Seeger H. Haas D. Forkel 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(3):349-350
The g-factor of the t1/2=9.3 ns, Iπ=5/2 + state at Ex=130 keV in77Br has been measured by observation of the time differential perturbed angular correlation (PAC) in a Co single crystal. The experimental value g=1.32(1) gives evidence for large deformation, which is discussed in the framework of triaxial-rotor-plus-particle models. 相似文献
18.
R. A. Brand P. Sen Ch. Sauer J. -P. Sanchez A. Rojek W. Zinn 《Hyperfine Interactions》1990,55(1-4):1243-1248
The valence of Bi and its substituents Sn and Sb are investigated in the high temperature superconductor (Bi0.8X0.15Sb0.05)2Sr2Ca2Cu3Oy (often denoted 2223) where X=Pb or Sn. Pb and Sn are isoelectronic with the valence states 2+ and 4+; Bi and Sb are as well with valence states 3+ and 5+. The valence state of Sn and Sb has been obtained from Mössbauer spectroscopy: they exist in the high charge states 4+ and 5+ respectively. Sn, Sb, and presumably Pb, take on the high valence state, and so furnish electrons to the conduction band. This is probably the reason why, although the (Pb, Sb)-doping aids in stabilizing the 2223 crystal structure, it is detremental to the electronic properties which lead to the superconducting phase. The valence state of Bi has been studied using X-ray photoelectron spectroscopy (XPS). These results show clearly that the Bi-based superconductor has a metal-like density of states at the Fermi level, and that the valence in the (Pb, Sb)-doped compounds is less than 3. This very surprising change in valence will have a profound effect on the superconducting properties, and is probably associated with the high valent states of Pb, Sn and Sb. 相似文献