Bi_2Sr_2CaCu_2Oy超导体无公度调制结构的研究

本文以Ｂｉ－Ｓｒ－Ｃａ－Ｃｕ－Ｏ体系（Ｂｉ系）中的Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏｙ（Ｂｉ２２１２相）超导体为对象，讨论了Ｂｉ２２１２超导体的平均结构，以及其平均结构与（存在着无公度调制的）实际结构之间的区别。论述了Ｂｉ系（着重于Ｂｉ２２１２相）超导体的无公度调制结构的起因，认为Ｂｉ系调制结构的起因主要是由于ＢｉＯ双层和钙钛矿层之间的晶格失配，更为合理的解释是：晶格失配是调制结构的起因，而额外氧是晶格失配的结果。     

元素替代对Bi_2Sr_2CaCu_2O_y单晶结构与超导电性的影响

选择过渡金属中磁性比较特殊的Ｍｎ替代Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏｙ（Ｂｉ２２１２相）中的Ｃｕ,采用自助熔剂法制备出Ｂｉ２Ｓｒ２Ｃａ（Ｃｕ１－ｘＭｎｘ）２Ｏｙ（ｘ＝０．０１,０．０５,０．０８,０．１）系列单晶。Ｘ射线衍射分析表明,单晶的ｃ轴长度随Ｍｎ含量的增加而减小。单晶的ａｂ面电阻率与温度变化的测量表明,零电阻温度Ｔｃ随Ｍｎ含量的增加而逐渐下降,超导电性被抑制。Ｍｎ元素替代Ｂｉ２２１２中的Ｃｕ所引起其结构与超导电性的变化,本文给出了较为合理的解释     

Pr掺杂对Bi_2Sr_2Ca_(1-x)Pr_xCu_2O_y单晶结构的影响

采用自助熔剂法制备出Ｂｉ２Ｓｒ２Ｃａ１－ｘＰｒｘＣｕ２Ｏｙ系列单晶样品,通过对样品的Ｘ射线衍射（ＸＲＤ）实验的结构分析,利用对称反射和对称透射几何得到沿单晶ａ、ｂ、ｃ方向的多级衍射,由此可以得到晶格参数和调制周期。本文给出了Ｂｉ２Ｓｒ２Ｃａ１－ｘＰｒｘＣｕ２Ｏｙ单晶的晶格参数ａ、ｂ、ｃ和调制周期ｓ随Ｐｒ掺杂量ｘ的变化,并讨论了这种结构细微变化的原因     

Ba和Mg掺杂对Bi（Pb）—Sr—Ca—Cu—O超导性能的影响

采用固态反应法制备了名义组分为Ｂｉ１．８Ｐｂ０．２Ｓｒ２Ｃａ２Ｃｕ３Ｏｘ和Ｂｉ０．９Ｐｂ０．１Ｂａ０．１Ｍｇ０．１Ｓｒ０．８ＣａＣｕ２Ｏｘ超导样品，并研究了Ｂａ，Ｍｇ掺杂对Ｂｉ系超导性能的影响。用Ｘ射线衍射及电阻－温度关系的测量获得的实验结果表明，添加Ｂａ和Ｍｇ元素可以有效地抑制Ｂｉ系２２１２相的生成，促进２２２３相的形成，并能提高超导材料的Ｔｃ。     

Sol-gel法合成Bi_(1.6)Pb_(0.3)Sb_(0.1)Sr_2Ca_2Cu_3O_x体系的超导材料的研究

本文用Ｓｏｌ－ｇｅｌ法合成了Ｂｉ１．６Ｐｂ０．３Ｓｂ０．１Ｓｒ２Ｃａ２Ｃｕ３Ｏｘ体系的高ＴＣ超导原粉，对于不同的烧结时间，材料的超导性有不同程度的差异，（超导转变温度为１０８．３～１１６．１Ｋ）并与同种方法合成的Ｂｉ１．７Ｐｂ０．３Ｓｒ２Ｃａ２Ｃｕ３Ｏｘ体系进行了比较．用Ｓｏｌ－ｇｅｌ法，在Ｂｉ系中掺杂Ｐｂ，同样会缩短烧结时间（缩短６０ｈ），促进高温相的形成，同时掺杂Ｐｂ，Ｓｂ，形成超导材料所需的烧结时间进一步缩短（缩短１５３ｈ）．利用ＳＥＭ和Ｘ－ｒａｙ观察和分析了样品的形貌特征和物相结构．Ｓｏｌ－ｇｅｌ法具有工艺简单，烧结时间短，样品颗粒均匀、粒度小、组分易控等优点，在高ＴＣ超导材料中不失为一种行之有效的材料制备工艺．     

钐（Ⅲ）与—2[（取代苯胺基）羰基]苯甲酸配合物的合成与表征

报道了８种２－［（取代苯胺基）羰基］苯甲酸与Ｓｍ（Ⅲ）配合物Ｓｍ（Ｐ）３．３Ｈ２Ｏ［其中Ｐ＝２－（ＣＯＯ）Ｃ６Ｈ４ＣＯＮＨＣ６Ｈ５－ｎＸｎ，Ｘ＝Ｈ，２－Ｃｌ，４Ｂｒ，２－ＣＨ３，３－ＮＯ２，２－ＯＣＨ３，２，４－二氯，３－ＯＨ，ｎ＝１，２］的合成，并用元素分析、红外光谱、电子反射光谱、热重分析进行了表征。结果证明了配位是通过羰酸羟基原子和酰胺羰基氧原子进行的，含３分子配位水。     

1673K下BaO-BaF_2-Cr_2O_3渣系的热力学性质

１６７３Ｋ下,采用－ＭｏＣｒ＋Ｃｒ２Ｏ３ＺｒＯ２（ＭｇＯ）｛Ｃｕ＋Ｃｒ｝ａｌｏｙ＋（Ｃｒ２Ｏ３）ｓｌａｇＭｏ＋固体电解质电池测定了ＢａＯＢａＦ２Ｃｒ２Ｏ３渣系中Ｃｒ２Ｏ３的活度．研究结果表明,Ｃｒ２Ｏ３的活度随其浓度升高而升高,随ＸＢａＯ／ＸＢａＦ２升高而降低．根据实验及Ｘ射线衍射结果推测了该渣系的等温相图,并作出了该渣系中Ｃｒ２Ｏ３的等活度图．     

铅掺杂Bi系超导体正电子寿命研究

在室温下测量了Ｂｉ２－ｘＰｂｘＳｒ２ＣａＣｕ２－ｘＭｇｘＯ８＋δ超导体的正电子寿命，发现正电子体寿命τｂ随着Ｐｂ含量ｘ的增加而减小；测量了转变温度Ｔｃ结果表明，Ｍｇ替换不影响电子结构，Ｐｂ替换使电子从Ｃｕ－Ｏ面迁移到Ｂｉ－Ｏ层，并导致ＣＵ－Ｏ面空穴浓度增加，转变温度Ｔｃ减小．     

N－间甲氧基苯基亚氨基二乙酸合铜（Ⅱ）二水化合物的晶体与分子结构

Ｎ－间甲氧基苯基亚胺基二乙酸合铜（Ⅱ）二水化合物［Ｃｕ（ＣＨ２ＣＯＯ）２ＮＣ６Ｈ４ＯＣＨ３］·２Ｈ２Ｏ属正交晶系，空间群Ｐｂｃａ，ａ＝１．０７２５（３），ｂ＝１．０８５１（４），ｃ＝２．１８２７（５）ｎｍ，ｖ＝２．５４０（２）ｎｍ３，Ｚ＝８，Ｍｒ＝３３６．８，Ｄｘ＝１．７６ｇｃｍ－３，μ＝１８．１ｍｍ－１，Ｆ（０００）＝１３７６。结构由直接法解出，偏离因子Ｒ＝０．０７８。Ｃｕ（Ⅱ）离子与亚氨基二乙酸分子中一个氮原子、两个水分子氧原子和两个羧基氧原子配位形成一变形四方单锥构型。Ｃｕ（Ⅱ）离子到四方单锥顶点Ｏ（７）原子（水２）的键长为２．２７９×１０－１（４）ｎｍ，长于配位基平面内Ｃｕ－Ｏ和Ｃｕ－Ｎ的平均键长［１．９３９×１０－１（４）和２．０５１×１０－１（４）ｎｍ］。     

Ca_8Zn（SiO_4）_4Cl_2：Eu~（2＋），Mn~（2＋）荧光体中Mn~（2＋）的晶晶学格位及Eu~（2＋）－Mn~（2＋）间能量传递

合成了Ｃａ８Ｚｎ（ＳｉＯ４）４Ｃｌ２：Ｅｕ（２＋），Ｍｎ（２＋）荧光体，对荧光体进行了结构和光谱的测试与分析．结果表明，Ｍｎ（２＋）优先占据四面体配位的Ｚｎ格位，Ｅｕ（２＋）－Ｍｎ（２＋）之间存在着有效的能量传递．     

化学改性二氧化锰结构表征

应用扩展X射线精细结构（EXAFS）技术及光电子能谱研究改性MnO2的结构,结果表明：掺杂原子进入了MnO2晶格中,锰的第一壳层配位数下降,并且增大高壳层配位原子的无序度。     

Sr2Mn2CuAs2O2的第一性原理计算研究

基于第一性原理计算,研究了3种不同结构的同组分物质Sr2Mn2CuAs2O2的电子能带结构及物质总能量,并探讨了Sr2Mn2CuAs2O2可能的最稳定结构.结果表明,3种不同结构的Sr2Mn2CuAs2O2材料均表现出金属性,且主要是具有Mn原子的层状结构起导电作用.其中同时含有CuO2层面与Mn2As2四面体层,并具...     

Imaging the granular structure of high-Tc superconductivity in underdoped Bi2Sr2CaCu2O8+delta.

Granular superconductivity occurs when microscopic superconducting grains are separated by non-superconducting regions; Josephson tunnelling between the grains establishes the macroscopic superconducting state. Although crystals of the copper oxide high-transition-temperature (high-Tc) superconductors are not granular in a structural sense, theory suggests that at low levels of hole doping the holes can become concentrated at certain locations resulting in hole-rich superconducting domains. Granular superconductivity arising from tunnelling between such domains would represent a new view of the underdoped copper oxide superconductors. Here we report scanning tunnelling microscope studies of underdoped Bi2Sr2CaCu2O8+delta that reveal an apparent segregation of the electronic structure into superconducting domains that are approximately 3 nm in size (and local energy gap <50 meV), located in an electronically distinct background. We used scattering resonances at Ni impurity atoms as 'markers' for local superconductivity; no Ni resonances were detected in any region where the local energy gap Delta > 50 +/- 2.5 meV. These observations suggest that underdoped Bi2Sr2CaCu2O8+delta is a mixture of two different short-range electronic orders with the long-range characteristics of a granular superconductor.     

High-Tc superconducting materials for electric power applications.

Large-scale superconducting electric devices for power industry depend critically on wires with high critical current densities at temperatures where cryogenic losses are tolerable. This restricts choice to two high-temperature cuprate superconductors, (Bi,Pb)2Sr2Ca2Cu3Ox and YBa2Cu3Ox, and possibly to MgB2, recently discovered to superconduct at 39 K. Crystal structure and material anisotropy place fundamental restrictions on their properties, especially in polycrystalline form. So far, power applications have followed a largely empirical, twin-track approach of conductor development and construction of prototype devices. The feasibility of superconducting power cables, magnetic energy-storage devices, transformers, fault current limiters and motors, largely using (Bi,Pb)2Sr2Ca2Cu3Ox conductor, is proven. Widespread applications now depend significantly on cost-effective resolution of fundamental materials and fabrication issues, which control the production of low-cost, high-performance conductors of these remarkable compounds.     

Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+delta.

Magnetic interactions and magnetic impurities are destructive to superconductivity in conventional superconductors. By contrast, in some unconventional macroscopic quantum systems (such as superfluid 3He and superconducting UGe2), the superconductivity (or superfluidity) is actually mediated by magnetic interactions. A magnetic mechanism has also been proposed for high-temperature superconductivity. Within this context, the fact that magnetic Ni impurity atoms have a weaker effect on superconductivity than non-magnetic Zn atoms in the high-Tc superconductors has been put forward as evidence supporting a magnetic mechanism. Here we use scanning tunnelling microscopy to determine directly the influence of individual Ni atoms on the local electronic structure of Bi2Sr2CaCu2O8+delta. At each Ni site we observe two d-wave impurity states of apparently opposite spin polarization, whose existence indicates that Ni retains a magnetic moment in the superconducting state. However, analysis of the impurity-state energies shows that quasiparticle scattering at Ni is predominantly non-magnetic. Furthermore, we show that the superconducting energy gap and correlations are unimpaired at Ni. This is in strong contrast to the effects of non-magnetic Zn impurities, which locally destroy superconductivity. These results are consistent with predictions for impurity atom phenomena derived from a magnetic mechanism.     

两种Cu(II)配合物的合成和结构表征(英文)

选取1,9—二(2—氟代苯基)—2,5,8—三氮杂壬烷与铜(Ⅱ)的苯甲酸盐和硝酸盐,合成了两个新的配合物[Cu(C18H23F2N3)(C7H5O2)(H2O)](C7H5O2)·2(H2O)(1)和[Cu(C18H23F2N3)(NO3)2]·(H2O)1/2(2),并获得其单晶,测定了晶体结构.单晶衍射数据显示化合物(1)属三斜晶系Pi空间群,化合物(2)属单斜晶系Cc空间群     

Imaging the effects of individual zinc impurity atoms on superconductivity in Bi2Sr2CaCu2O8+delta

Although the crystal structures of the copper oxide high-temperature superconductors are complex and diverse, they all contain some crystal planes consisting of only copper and oxygen atoms in a square lattice: superconductivity is believed to originate from strongly interacting electrons in these CuO2 planes. Substituting a single impurity atom for a copper atom strongly perturbs the surrounding electronic environment and can therefore be used to probe high-temperature superconductivity at the atomic scale. This has provided the motivation for several experimental and theoretical studies. Scanning tunnelling microscopy (STM) is an ideal technique for the study of such effects at the atomic scale, as it has been used very successfully to probe individual impurity atoms in several other systems. Here we use STM to investigate the effects of individual zinc impurity atoms in the high-temperature superconductor Bi2Sr2CaCu2O8+delta. We find intense quasiparticle scattering resonances at the Zn sites, coincident with strong suppression of superconductivity within approximately 15 A of the scattering sites. Imaging of the spatial dependence of the quasiparticle density of states in the vicinity of the impurity atoms reveals the long-sought four-fold symmetric quasiparticle 'cloud' aligned with the nodes of the d-wave superconducting gap which is believed to characterize superconductivity in these materials.     

Cr, Li, W等添加物对瓷介电容瓷料性能的影响

研究了Cr2O3,Li2CO3,WO3对于0.90(Sr0.54Pb0.26Ca0.20)TiO3-0.1Bi2O3*3.5TiO2为系统的中高压瓷介电容瓷料的介电性能的影响,实验发现掺加Cr2O3对于该瓷料的ε-t曲线有压峰作用;而Li2CO3的掺加有提升ε-t峰作用,介电常数随着掺加量的增加而提高,损耗在45 ℃以下随掺加量的增加而提高;WO3的添加也具有提峰作用,并且同时可以降低高温段ε的温度系数.     

在石墨炉内石墨探针表面上的原子化机理研究XI.硝酸铋的原子化机理

研究了硝酸铋在石墨炉内石墨探针表面上的原子化机理，结果表明．硝酸铋首先分解为氧化铋，后者被碳还原生成铋，铋再蒸发进入气相，经历二聚体，尔后分解为气态铋原子。