La2O3—BaO系复氧化物的现场拉曼光谱研究

对于Ｌａ０．２Ｂａ０．８－ｘＣａｘ（Ｏ，ＣＯ３）其中ｘ＝０．０、０．２、０．４、０．６氧化物在９７３Ｋ及甲烷氧化偶联（ＯＣＭ）条件下，无Ｃａ＾２＋的样品可用表面ＢａＣＯ３和（ＬａＯ）２ＣＯ３的Ｒａｍａｎ谱及８１０ｃｍ＾－１附近的Ｏ２＾２－特征峰来表征；含Ｃａ＾２＋的样品，则表现了混合碳酸盐（Ｃａ，Ｂａ）ＣＯ３的特征，还有位于１１３５ｃｍ＾－１（ｗ）和８１０ｃｍ＾－１（ｗ）的Ｏ２＾－、Ｏ２＾２－瞬时     

Tl—1223超导体及其复Ag带的制备

研究了用产中分熔化法制备Ｔｌ－１２２３超导体的工艺。样品的名义组成为（Ｔｌ０．５Ｐｂ０．５）（Ｓｒ０．８Ｂａ０．２）Ｃａ２Ｃｕ３Ｏｙ。经熔化退火的样品，其磁化电流的７７Ｋ和１Ｔ下大于２×１０＾４／ｃｍ＾２。用熔化－退火的超导粉作原料制得的复Ａｇ带短样，Ｊｃ达１．６－１．７×１０＾４Ａ／ｃｍ＾２（７７ｋ，０Ｔ）。采用烧结后的超导粉作原料，在制备复Ａｇ带的工艺中，如用熔化－退火的热处理制度，可以免除…     

Bi2.2Sr1.8Ca1.05Cu2.15—xNaxO8＋y超导电性研究

本介绍了用熔融法制备Ｂｉ２．２Ｓｒ１．８Ｃａ１．０５Ｃｕ２．１５－ｘＮａｘＯ８＋ｙ（ｘ＝０，０．４～０．８）样品，发现诸样品零电阻温度都在９０Ｋ左右，其中ｘ＝０．７，Ｔｃ０达到９２．５Ｋ。在８１Ｋ较高温区，该类样品仍然表现出良好的超导电性，其临界电流密度还达到１０＾３Ａ／ｃｍ＾２量级。     

对Bi-2212超导体中的Raman谱指认

本文对Ｂｉ２－ｘＰｂｘＳｒ２ＣａＣｕ２Ｑδ（ｘ＝０￣０．５）系列样吕以及在真空下不同温度退火的Ｂｉ１．６Ｐｂ０．４Ｓｒ２ＣａＣＵ２Ｏδ样品进行了Ｘ射线衍射和Ｒａｍａｎ谱实验研究。测量表明,随着退火温度的升高,ａ,ｂ,ｃ轴晶格常数增加,与Ｏ（１）ＣｕＢｇ模式相关的２９４ｃｍ＾－１的峰强减少,峰位红移。研究结果进一步表明,４６４ｃｍ＾－１和６３０ｃｍ＾－１峰分别与Ｏ（３）ＢｉＡ１ｇ和Ｏ（２）ＳｒＡ１ｇ     

Y1—xNdxSr2Cu2.7Mo0.3O7—δ体系的拉曼和红外光谱研究

利用拉曼散射和红外有收光谱研究了Ｙ１－ｘＮｄｘＳｒ２Ｃｕ．０ｍＯ０．３ｏ７－δ系列样品的声子振劝性质，实验结果表明，对ｘ＝０的样品，在拉曼光谱中主要出现２３２３，４４３，５２２和５７８ｃｍ＾－１几个特征峰，在中红外吸收光谱中出现５２２，５８０和６４６ｘｍ＾－１特征峰。     

Rb3C60超导薄膜的电输运性质

在成功制备Ｃ６０外延薄膜的基础上，我们又尝试了碱金属Ｒｂ对该膜的掺杂。结果表明，从室温至８０Ｋ左右，Ｒｂ３Ｃ６０薄膜的电阻温度系数大于０，并近似符合公式：ρ（Ｔ）＝ａ＋ｂＴ＾２，与单晶样品一致。但是，当温度低于８０Ｋ以后，出现了弱的对数局域。在５Ｋ、零场下，样品的Ｊｃ值一般为１０＾３－１０＾４Ａ／ｃｍ＾２，且有如下规律：Ｊｃ（Ｔ）＝Ｊｃ（０）（１－Ｔ／Ｔｃ）＾ａ，α＝１．３－２．０。此外，我们还测     

用光谱学方法研究不同放电等离子体粒子约束

本文用光谱学方法研究在ＨＬ－１装置上ＬＨＣＤ及ＥＣＲＨ等离子体，弹丸注入等离子体，偏压电极与偏压孔栏等离子体粒子约束特性。结果表明：在弹丸注入使用正向偏压电极与偏压孔栏期间，等离子体粒子约束行到改善，较低密度下（＾ｎｅ＜２．０×１０＾１＾３ｃｍ＾－＾３），ＬＨＣＤ脉冲期间粒子约束得到改善；而当密度＾－ｎｅ大于２．０×１０＾１＾３ｃｍ＾－＾３时，等离子体约束变坏。ＥＣＲＨ脉冲期间粒子约束得不到改善。     

Y_（1－x）Nd_xSr_2Cu_（2．7）Mo_（0．3）O_（7－δ）体系的拉曼和红外光谱研究

利用拉曼散射和红外吸收光谱研究了Ｙ１－ｘＮｄｘＳｒ２Ｃｕ２．７Ｍｏ０．３Ｏ７－δ（ｘ＝０，０．２，０．５，０．８，１．０）系列样品的声子振动性质。实验结果表明，对ｘ＝０的样品，在拉曼光谱中主要出现３２３，４４３，５２２和５７８ｃｍ－１几个特征峰，在中红外吸收光谱中出现５２２，５８０和６４６ｃｍ－１特征峰。随着样品中Ｎｄ组分的增加，３２３ｃｍ－１峰向低波数发生位移，而５２２和６４６ｃｍ－１峰则向高波数发生位移。本文对这些振动模进行了指认，并对其随不同样品组分的变化行为进行了讨论     

MOCVD法在金属基体上制备YBCO超导带

本报道了用ＭＯＣＶＤ静态和动态沉积两种工艺制备ＹＢＣＯ超导带的实验结果。以Ｙ（ＴＭＨＤ）３、Ｂａ（ＴＭＨＤ）２和Ｃｕ（ＴＭＨＤ）２为挥发源，Ｏ２气为反应剂，高纯Ａｒ气为载流气体，在静止和以１０－１５ｃｍ／ｈ带速移动的金属银基体上，制出了有强烈ｃ－轴取向的ＹＢＣＯ超导带。静态沉积样品的Ｊｃ达到１．０４×１０＾４Ａ／ｃｍ＾２，动态沉积样品的Ｊｃ达到１．４×１０＾４Ａ／ｃｍ＾２（７８Ｋ，０Ｔ）。对改…     

Bi2201体系中Raman散射、微结构和输运性质研究

利用Ｘ－光衍射,电子衍射,Ｒａｍａｎ散射和电阻率等手段对多晶样品Ｂｉ１．８Ｐｂ０．２Ｓｒ２Ｃｕ１－ｘＦｅｘＯｙ,Ｂｉ１．８Ｐｂ０．２Ｓｒ１．６＋ｘＬａ０．４－ｘＣｕ１－ｘＦｅｘＯｙ的结构和性能进行了研究。结果表明：Ｂｉ２２０１体系的调制特征与客外氧的多少无关,６２５ｃｍ＾－１附近的Ｒａｍａｎ峰受‘电荷转移’效应和调制结构变化的显著影响,晶体的微结构变化强烈影响体系的超电性和输运性质。     

Oxygenation-induced two peaks in the self-doped La0.9MnO3+δ compounds

A series of self-doped La_0.9MnO_3+δ compounds have been fabricated by the solid-state reaction method with different post-annealing and oxygenation processes. The temperature dependence of resistivity measured at several magnetic fields indicated that all of these samples have an insulator–metal transition with a large negative colossal magnetoresistance (CMR) ratio. The resistivity, maximum CMR ratio and peak position are dominated by the oxygen content. As the oxygen content increases, the resistivity decreases, the peak position shifts to higher temperature and the maximum CMR ratio increases, respectively; meanwhile the peak number in the R–T curve is changed from 1 to 2, then from 2 to 1. The temperature dependencies of magnetization and specific heat show the evidence of magnetic phase transition in these samples. We think that two peaks contributed by the different oxygen-induced ferromagnetic phases resulted in the phase separation of the sample.     

Phase transformation in (0.90−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3-0.10PbZrO3 piezoelectric ceramic: X-ray diffraction and Raman investigation

Piezoelectric ceramics with compositions of (0.90−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃-0.10PbZrO₃, x=0.28, 0.31, 0.34, 0.37, 0.40 and 0.43, were prepared using the conventional columbite precursor method, and their structural phase transformation and piezoelectric behaviors near the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO₃ content. X-ray diffraction (XRD) results demonstrate that the structure of the ceramics experiences a gradual transition process from rhombohedral phase to tetragonal phase with the increasing of PbTiO₃ content, and that compositions with x=0.34-0.40 lie in the MPB region of this ternary system. A Raman spectra investigation of the ceramic samples testified to the transformation process of rhombohedral phase to tetragonal phase by comparing the relative intensities of tetragonal E(2TO₁) mode and rhombohedral phase R_h mode. The structure information was also correlated to the parabola change of the piezoelectric constant; the maximum piezoelectric constants were obtained near the MPB region.     

Phase transition and superconductivity of (Ba,Sr,La)2YCu3Oz (z>6.9)

A series of (Ba,Sr,La)₂YCu₃O_z (z>6.9) samples is studied to elucidate the relationship between structure, cation composition and oxygen content. The concentration of La plays an important role in the orthorhombic to tetragonal phase transition. The tetragonal structure is stabilized by increasing oxygen content and decreasing average ionic radius of cations on the Ba site. The phase transition is explained in terms of the random distribution of CuO₅ pyramids in the BaO–CuO_x slab. Superconductivity does not depend significantly on the phase transition.     

YBa2Cu3-xFexOy的离子配位与结构转变

本文用穆斯堡尔效应、X射线衍射等手段,系统研究了掺铁的YBa₂Cu_3-xFe_xO_y(0.01≤x≤0.2)超导氧化物经过不同温度真空退火后超导转变温度T_c、相结构、氧含量与氧配位之间的关系,结果表明,铁主要占Cu(1)位,铁含量的增加和高温真空退火都引起正交相向四方相转变,T_c逐渐减小至零,但这两种转变过程的铁的配位结构和氧含量却不相同,对前者,相变是与出现相当数量的六配位F 关键词：     

Anomalous magnetostrictive effects in （La1—xTbx）2／3Sr1／3 MnO3

A series of (La_{1-x}Tb_x)_{2/3}Sr_{1/3}MnO_3 polycrystalline samples has been studied by means of x-ray diffraction, magnetostriction, and thermal expansion measurements. It has been found that this series undergoes a phase transition from a rhombohedral to an orthorhombic form at the doping level x≈0.20 at room temperature accompanied by an anisotropic magnetostriction up to －50×10^{-6} under a magnetic field of 1T. The linear and volume magnetostrictions vary with chemical composition, even change sign. At T=80K, the magnetostrictions for the samples of x=0.20 and 0.40 exhibit different behaviours. The sample of x=0.20 has positive volume and linear magnetostrictions and a negative anisotropic magnetostriction, while the sample of x=0.40 has an opposite behaviour. The magnitude of volume magnetostriction for both the samples is essential (～10^{-4}) at T=80K under a magnetic field of 4T. We conclude that these anomalous effects are due to the charge delocalization and the structural phase transition between orthorhombic and rhombohedral forms induced by the applied magnetic field.     

(Bi,Pb)2Sr2Ca2Cu3Oy单相样品的超导电性与载流子浓度

对(Bi,Pb)₂Sr₂Ca₂Cu₃O_y单相样品进行不同条件下的热处理,通过X射线衍射、电阻-温度关系、交流磁化率,以及Hall系数等测量,发现样品均具有较好的单相性,随着热处理条件的变化,其超导转变中点温度(T_c)有规律地分布在100—110K之间,T_c随载流子浓度(n_H)的增加而升高。实验结果表明,热处理条件对样品的相结构、超导 关键词：     

The effect of oxygen stoichiometry on electrical transport and magnetic properties of La0.9Te0.1MnOy

The effect of the variation of oxygen content on structural, magnetic and transport properties in the electron-doped manganites La_0.9Te_0.1MnO_y has been investigated. All samples show a rhombohedral structure with the space group The Curie temperature T_C decreases and the paramagnetic-ferromagnetic (PM-FM) transition becomes broader with the reduction of oxygen content. The resistivity of the annealed samples increases slightly with a small reduction of oxygen content. Further reduction in the oxygen content, the resistivity maximum increases by six orders of magnitude compared with that of the as-prepared sample, and the ρ(T) curves of samples with y=2.86 and y=2.83 display the semiconducting behavior (dρ/dT<0) in both high-temperature PM phase and low-temperature FM phase, which is considered to be related to the appearance of superexchange ferromagnetism and the localization of carriers. The results are discussed in terms of the combined effects of the increase in the Mn²⁺/(Mn²⁺+Mn³⁺) ratio, the partial destruction of double exchange interaction, and the localization of carriers due to the introduction of oxygen vacancies in the Mn-O-Mn network.     

Nd_(0.9)Ca_(0.1)Ba_2Cu_3O_(6+x)(x=0～1)超导体系的Raman光谱研究

Ｎｄ０．９Ｃａ０．１Ｂａ２Ｃｕ３Ｏ６＋ｘ（ｘ＝０～１）超导体系的Ｒａｍａｎ光谱研究赵芸１罗培勋２左健２许存义２李晓光２（１安徽机电学院芜湖２４１０００）（２中国科学技术大学结构分析开放研究实验室合肥２３００２６）ＳｔｕｄｙｏｎｔｈｅＲａｍａｎＳｐｅ...     

Structural and physical properties of CaFe2As2

Polycrystalline and single crystalline samples of CaFe₂As₂ were prepared by using different fabrication routes. These samples show evident differences in both phase transition temperatures and transport properties depending on fabrication conditions. TEM observations reveal a rich variety of structural phenomena in these materials, such as a tweed-like pattern in self-flux samples, a structural modulation along the 〈1 1 0〉_tetra direction in the polycrystalline sample, and complex dislocation networks in the Sn-flux samples. Careful analysis shows that the twinning domains arising from the tetragonal-to-orthorhombic phase transition belong to the δ-type.     

GdBaCo2O5+δ体系的滞弹性内耗研究

GdBaCo₂O_5+δ体系的低频内耗研究表明：体系中存在一个由额外氧运动引起的弛豫内耗峰；额外氧δ对这个弛豫内耗峰的大小、峰形及峰位有较大影响，反映了额外氧状态随δ而变化.当δ=0.005，体系中额外氧含量很少而接近零时，相应的内耗峰消失；δ达到一定数量后，出现弛豫内耗峰.由δ=0.278，0.407，0.421，0.515样品的弛豫内耗峰分析可得到体系随δ不同存在着三种不同的额外氧形态.此外，δ=0.421及0.515的样品在360K附近存在一个相变内耗峰，它对应着体系中的金属—绝缘体转变. 关键词： 2O_5+δ')" href="#">GdBaCo₂O_5+δ 额外氧 内耗峰