Bi(Pb)-Sr-Ca-Cu-O体系中110K超导相的制备和结构研究

The stable superconducting phase with T_c 110 K has been prepared in samples of nominal composition (Bi_(2-x)Pb_x)Sr_2Ca_2Cu_3O_y and (Bi_(2-x)Pb_x)Sr_2Ca_3Cu_5O_y x=0.2, 0.4, 0.6. The crystal strucuure of the superconducting phase (Bi_1.8Pb_0.2)Sr_2Ca_2Cu_3O_y with T_c 106.3 K has been determined in the sample of nominal composition (Bi_1.8Pb_0.2)Sr_2Ca_3Cu_5O_y. It is a nine decker perovskite arrangement by incorporating two extra layers CaCuO_2 in each cell of Bi_2Ca_1Cu_2O_y. The plane of CuO_2 is planar in incorporating layer CaCuO_2. Speace group D~1_(2h)-Pmmm was assigned. Adding Pb is in Bi site, and atomic radius and atomic valence in Bi site was modified, so that it is able to stabilize crystal structure and progress superconducting properties.     

高价离子掺入Bi(Pb)-Sr-Ca-Cu-O体系对成相和结构的影响

The effects of high valence cations M~(n+) (n≥4) doped on the phase formation and the structure stability have been investigated. In the crystal structure X_2Sr_2Ca_2Cu_3O_(10)(X = Bi_(1-x-y)Pb_xM_y), the high valence cations M~(n+), Bi~(3+), and Pb~(2+) were deter-mined to statistically distribute at the bismuth positions. The bismuth valence is raised and the positions of oxygen atoms in the (XO_2X) double layers are fully occupied. Conseqently, The structural stability is increased. The phase 2223 was found to form more rapidly by doping and the single phase with T_c(0)>110 K can be obtained more easily.     

高价离子掺入Bi(Pb)-Sr-Ca-Cu-O体系对成相和结构的影响

Sunshine等在Bi-Sr-Ca-Cu-O体系中掺入少量Pb~(2+)后,可获得T_(c(0))=110K以“2223”相为主的样品.其后,Shun-ichi、卢伟京等也得到同样的结果,但都需要长达300～500小时烧结,所得到的样品仍含有少量“2212”相、我们拟对Bi(Pb)-Sr-Ca-Cu-O体系掺入高价离子,M~(n+)(n≥4),如Sn~(4+),Sb~(5+),Mo~(6+),W~(6+),研究它们对“2223”成相和结构的影响。     

(Bi,Pb)-Sr-Ca-Cu-O体系的成相规律和共生现象的研究

本文通过高温X射线衍射、差热分析(DTA)和非晶态的结晶等手段系统地研究了Bi系超导材料的成相规律。观察到了Bi系中2201,2212和2223相之间的相互转变,解释了2201,2212和2223相共生的原因。在2223相的形成过程中,2212相与Ca_2CuO_3相存在成分平衡以及2212,Ca_2CuO_3和2223相之间热力学稳定的竞争,这也是2223相难以制备的原因。掺Pb的主要作用是以Ca_2PbO_4代替Ca_2CuO_3,从而避免了上述的成分平衡和热力学稳定的竞争。     

Study on Phase-Formation Mechanism and Intergrowth for Bi(Pb)-Sr-Ca-Cu-O System

In this paper, the phase-formation mechanism of Bi-based superconductors was systematically investigated by using high-temperature X-ray diffraction, differential thermal analysis (DTA) and crystallization of amorphous state. The transformations among Bi-based 2201, 2212 and 2223 phases were observed, and the intergrown phenomenon of the 2201, 2212 and 2223 phases was explained. It was proposed that there exist a composition equilibrium between 2212 phase and Ca2CuO3 and a competition of thermody-namic stability among Ca2CuO3, 2212 and 2223 phases. This is why it is difficult to prepare the 2223 phase. After Pb was doped in Bi-Sr-Ca-Cu-O system, Ca2CuO3 phase in the Bi-Sr-Ca-Cu-O system was replaced by Ca2PbO4, so that the composition equilibrium and competition of thermodynamic stability mentioned above were avoided.     

超导相(Bi1.7Pb0.2In0.1)Sr2Ca2Cu3O10的制备和晶体结构研究

The superconducting phase(Bi_(1.7)Pb_(0.2)In_(0.1))Sr_2Ca_2Cu_3O_(10) with on-set T_c near 112K and zero resistivity at 95K has been prepared. The Unit cell is. body-centered tetragonal, space group I4/mmm, a=0.3.817(1) nm, c=3.704(1) nm. Chemical substitution of Pb and In in Bi—Sr—Ca—Cu—O series results in the growth of 2223 phase. The superconductivity and the formation mechanism are associated with the structural features.     

Pb(Ⅱ)离子印迹吸附剂的制备及固相萃取性能研究

采用表面印迹技术,结合溶胶凝胶过程,合成了巯基功能化的Pb(Ⅱ)离子印迹吸附剂,利用傅立叶变换红外光谱和N2吸附-脱附对其进行了表征,并用平衡吸附实验研究了其固相萃取性能.结果表明,该印迹吸附剂对Pb(Ⅱ)的结合能力和选择性明显高于非印迹吸附剂,并且具有较快的吸附速率,20 min即达到吸附平衡,最大的平衡吸附量达221 mg/g,在Cd(Ⅱ)存在下,相对选择性系数达到121.该法的检出限为0.23 μg/L,相对标准偏差为3.7%.将该印迹吸附剂用于实际水样的分离富集和测定,结果令人满意.     

Bi系中2212相的超导电性研究

已知在Bi系高Tc超导体中存在三个超导相:2223相的Tc～110k,c～37(?);2212相的Tc～85k,c～30.6(?);2201相的Tc～10k。在实验过程中,我们注意到还可能有另外的超导相存在,通过改变元素名义配比和制备工艺观察到一个具有2212相结构,但Tc却表现为～105k的新现象存在。 实验部分 样品制备采用固相反应方法将Bi_2O_3、PbO、Sb_2O_3、SrCO_3、CaCO_3、CuO(均为A.R.级)混匀、碾磨,于～810℃在刚玉坩埚中预烧20h;再碾,压片后于～870℃在磁舟中烧结60-240h,然后作测试分析。     

HCOO在Cu(110)、Ag(110)和Au(110)表面的吸附

采用密度泛函理论(DFT)以及广义梯度近似方法(GGA)计算了甲酸根(HCOO)在Cu(110)、Ag(110)和Au(110)表面的吸附. 计算结果表明, 短桥位是最稳定的吸附位置, 计算的几何参数与以前的实验和计算结果吻合. 吸附热顺序为Cu(110)(-116 kJ·mol-1)>Ag(110)(-57 kJ·mol-1)>Au(110)(-27 kJ·mol-1), 与实验上甲酸根的分解温度相一致. 电子态密度分析表明, 吸附热顺序可以用吸附分子与金属d-带之间的Pauli 排斥来关联, 即排斥作用越大, 吸附越弱. 另外还从计算的吸附热数据以及实验上HCOO的分解温度估算了反应CO2+1/2H2→HCOO的活化能, 其大小顺序为Au(110)>Ag(110)>Cu(110).     

金属离子Bi(Ⅲ)络合物体系的极谱法研究

The B（i Ⅲ）-Ligand（pyridine-2-carboxylic acid）system was studied by the differential pulse polarography（DPP）at the fixed total-ligand to total-metal concentration ratio［LT］:［MT］and varied pH. An appropriate model for the metal complex system is designed according to polarographic peak parameters,that is,the observed shift in the peak potential and the change in the peak current with pH changes in the sample solution. The polarographic experimental complex formation curve（ECFC）and theoretical complex formation curve（TCFC）were used for checking the designed metal complex model as well as optimizing stability constants. The ECFC,in which experimental parameters（a shift in a peak potential and a variation in a peak current）are included,appears to be a characteristic function for a particular metal-ligand system. The TCFC is a theoretical curve calculated from massbalance equations for the designed metal-ligand model. Using the computer analytical program,stability constants of metal complexes and species distribution diagrams are obtained by solving the mass-balance equations written for the metal complex system and fitting the complex formation curve. Five bismuth complexes MHL,ML,ML2,ML3,ML3 （ OH）,and their stability constants as logβ 7.52±0.15,7.48±0.06,13.94±0.02,18.12±0.03 and 26.78±0.03,respectively,are finally reported while the TCFC fits best the ECFC.     

Ba—K—Bi—O和Ba—K—Pb—O氧化物的磺量滴定

本文提出了碘量法滴定Ｂａ－Ｋ－Ｂｉ－Ｏ和Ｂａ－Ｋ－Ｐｂ－Ｏ氧化物中Ｂａ和Ｐｂ的名义价态，然后据此计算这些氧化物中Ｋ和Ｂａ含量的方法。     

均相催化中的结构研究(摘要)

在许多金属催化的有机反应中,能形成金属杂环化合物,举二类反应为例。 1.炔-烯的共齐聚反应炔类的环三聚反应,早已发现。一般用镍催化剂:但是,要使二份炔和一份烯及应而成环己二烯衍生物:则不易达到,因有一竞争反应,所得主要为三份炔的环聚物。有人假设这一反应的中间体是金属杂环化合物(Ⅰ):     

Pb(Ⅱ)水合结构的密度泛函及分子动力学研究

水溶液中Pb(Ⅱ)的水合结构缺乏实验数据,成键机理尚不明确.采用密度泛函理论、周期性边界计算水合物种Pb(HO)2+1-9的低能构象,探讨其结合能和稳定性,结合该离子在水溶液中的第一性原理分子动力学弛豫行为和扩展X射线吸收精细结构(EXAFS)谱特征,确定其最佳稳定构型和水合数,并通过Mulliken电荷布居、分波态密度及差分电荷密度分析其成键机理.低能优化结果表明,水合数6,7和8的构象均有可能存在,动力学弛豫过程Pb(Ⅱ)的第一和第二水合层不存在明显分界,其优势构型的水合数为6,属于偏半方位构型.22 6Pb(HO)+中Pb—O键的离子性较强,成键机理主要为Pb6p6d轨道与Pb6s-O2p反键态轨道进行耦合,存在反键态电子填充,表现为原子间电子密度的减少.     

高T_c LaBa_2Cu_3O_(7-δ)超导相的制备和结构研究

我国蕴藏着丰富的稀土元素,利用镧代替钇,研究高T_c超导体具有一定的经济意义。但镧和钡的原子半径相近而比钇大得多,这给制备工作带来了困难。国内曾有几个单位制备出了T_c80K的超导相,但都难以重复。日本A.Maeda等人合成了T_c80K的正交LaBa_2Cu_3O_(7-δ)超导相,测定了晶体结构和相转变温度。最近我们也开展了对这个体系的研究,本文将给出隐定的高T_cLaBa_2Cu_3O_(7-δ)超导相的制备方法、相变温度、晶体结构以及超导性能与正交性的关系。     

高价离子掺杂对Bi系成相和结构的影响(II)

In our previous work we have found that the 2223 phase is formed more rapidly and the structural stability can be enhanced by doping high valence cation(Sn~(4+)、Sb~(5+)、V~(5+)、W~(6+)、Mo~(6+) etc.) in the Bi(Pb)SrCaCuO system. In this paper the effects of high valence cations doped on the phase formation and the crystal structure are discussed further.The Aurivillus building and rocksalt building unit coexist in the Bi double layers. The structural variety strongly affects the structural stability. Owing to Pb~(2+) addition the probability of Aurivillus building is increased, the stability of 2223 phase can be promoted. However, the structure is still not stable, since the addition of Pb~(2+) has decreased the valence state of Bi site and the oxygen positions are not fully occupied. By doping high valence cation, especially, when the valence of Pb_x~(2+)M_y~(n+) equals to +3 the structure of the 2223 phase can be stabilized. This result has been observed with examining elemental content of 2223 phase.The melting point of the grain boundaries are much lower after doping high valence cations, therefore the ion diffusion is more rapid and acceleration of the 2223 phase formation is observed.     

磁光薄膜材料的微量化学分析法——(Pb Bi Pr Yb Gd)_3(Fe Al)_5O_(12)、(Pb Bi Tm Fe Ga)_8O_(12)原子比值

掺铋石榴石单晶薄膜是一种性能良好的磁光材料。薄膜组成影响材料的性能。国外用放射性示踪等方法测定其组成。本文解决了取样问题,应用层析分离与分光光度法测定铁、铝、铋、镓、镨、钇、镱与铥含量;并确定了薄膜组份的原子比值。 1.酸腐蚀法取样:本文在工作的基础上,样品用浓HNO_3和24NH_2SO_4混合酸(1:3)加热溶解约需数分钟。 2.铝-铬天青S-溴化十六烷基吡啶分光光度法:本文采用醋酸丁酯在7NHCI中萃取     

Ni(110)上氯和氧共吸附表面的结构和性质

用XPS,UPS,AES和功函数测定等方法考察了氯和氧在Ni(110)上的共吸附。氯强烈阻碍了氧的接续吸附;相反,氯接续吸附的速度和吸附量却因氯能驱使预吸附的氧溶入体相而没有明显影响。角分辨XPS分析为这一共吸附模型提供了进一步的证据。共吸附表面上氯和氧的热脱附和两者单独在Ni(110)表面上热脱附过程相似,但两者的脱附温度都有明显的降低。对共吸附和热脱附的机理进行了详细的讨论。     

高价离子掺杂对Bi系成相和结构的影响(Ⅱ)

Sunshine等在BiSrCaCuO体系掺入Pb~(2+)取代部分Bi,经较长时间灼烧后.获得T_(c(0))?110 K以2223相为主的样品,Hongbao等又报导了用Sb部分取代Bi(Pb)SrCaCuO体系中的Bi的研究结果.我们曾用Sb~(5+)、Sn~(4+)、W~(6+)、Mo~(6+)等高价离子部分取代Bi,研究这些离子对BiSrCaCuO体系成相的影响,发现掺高价离子后2223相易于生成并易于得到T_(c(0))?111K的超导体.本文则进一步探讨高价离子掺入的影响及其加速2223相生成的原因。     

超导相YBa_2Cu_3O_(7-d)的制备与结构研究

本文按计量式Y_(0.334)Ba_(0.666)CuO_(3-y)制备和得到了题目超导物相的样品。实验中使用柠檬酸为复合剂显著改善了金属氧化物的分散性和超导物相的均匀性。我们发现制备所得样品中,偏离四方晶格愈甚者,其超导性能愈佳。由X射线粉晶衍射数据测定了晶体结构,确认了金属离子的化学计量比和给出了氧原子的位置。正交或假四方晶胞的晶胞参数为a=3.893,b=3.813和c=11.867。晶胞由铜原子占据顶点位置的三个钙钛矿型立方体所组成,二个钡原子居于上层和底层的两个体心位置,而钇原子则占据居中立方体的体心位置。氧原子均占据诸立方体的稜心位置,但001/2处为空位,而01/20处的空位则导致晶格对称性由四方畸变为正交,这一畸变对超导相有深远的影响。钇和钡原子的配位多面体系由立方-八面体所派生的八配位和十配位的多面体,两者分别与移去晶胞中001/2和01/20处的氧原子后的氧多面体相对应。根据键价理论,以Y—O,Ba—O和Cu—O键长为基础,我们合理地论述了,即使在001/2及01/20处氧缺位的情况下,1/200处氧原子的占有率亦将低于1,与晶胞对应的该物相化学式为YBa_2Cu_bO_(7-d),0.2相似文献   

含氢键相互作用的IPN体系(Ⅴ)——体系组成变化对相结构和性能的影响

研究了含引入氢键的PBA和PS(OH)组成的IPN体系,PS(OH)为含羟基的改性聚苯乙烯.与相应的非交联聚合物的共混体系不同,IPN均显示两相结构,一相几乎为纯PBA,另一相则是混合相;仅当PS(OH)中羟基含量高达30mol％且其为IPN的主要成分时,才有相当量的PS(OH)溶入PBA为主的相.IPN的模量-组成行为可用Budiansky方程描述,表明两相的连续性,这一结论与透射电子显微镜的观察一致.