Bi-Ca-Sr-Cu-O体系中的高温超导电性

本文报道掺Pb和不掺Pb的Bi-Ca-Sr-Cu-O体系中高温超导电性的变化规律,讨论了体系组成、制备条件、物相与超导电性的关系。在合适的制备条件下,Bi-Pb-Ca-Sr-Cu-O体系中所形成的T_(ce)为103K的物相,除个别衍射峰外,几乎与纯铋系的4334相完全一致。

氧化物超导体BiSrCaCuO的霍尔效应(英文)

对名义组分为BiSrCaCu_2O_y的超导氧化物进行了霍尔系数、直流电阻率和磁阻测量。发现霍尔系数为正,且当样品处于正常态时它保持不变。由此算得的载流子浓度约为36.×10^(21)/cm^3。结合正常态时线性的的电阻-温度关系,作者认为此材料的能带结构可能属于类自由空穴型的简单带结构。还对颗粒超导电性的问题进行了讨论。

YBa_2Cu_(3-x)M_xO_(7-y)体系的结构和热稳定性及电子局域化

测定了系列单相样品YBa_2Cu^(3-x)M_xO_(7-y)(M=Zn,Co,Ni)的结构参数,热分解温度和电阻一温度关系。结构分析表明Zn在一定范围内有序地取代Cu,而Co和Ni的取代则是无序的。超导电性与有序取代和无序取代有很强的关联。随着x值的增加,热稳定性逐渐降低,电子局域性增加,Tc下降,四者之间存在密切的关系。作者用晶格的不稳定性解释了这一事实。

HALL EFFECT IN SUPERCONDUCTING OXIDE Ba-Y-V-Cu-O

Results of resistivity,ac magnetic susceptibility,and Halleffect measurements for Ba_(1.2)Y_(0.9)V_(0.9)Cu_(3)0_(7-δ)are reported.The positive value of Hall constant indicates that the material conducts via holes with a carrier concentration of 1.6×10^(21)cm^(-3)at room temperature.A large anomaly in RH near Tc is observed.

ZERO RESISTANCE ABOVE 90K IN SUPERCONDUCTING OXIDE Tm-Ba-Cu-O

Superconducting transition has been observed by electrical resistance and a.c.magnetic susceptibility measurements in Tm_(x)Ba_(1-x)CuO_(3-y) with x=0.6 and 0.7 and y>0.The highest T_(c) of the samples measured is observed in Tm_(0.6)-Ba_(0.4)CuO_(3-y) which has the T_(c)(mid)=91K with ΔT_(c)=0.5K,and T_(c)(ρ=0)=90.1K.The a.c.magnetic susceptibility measurements show a very strong diamagnetism at the temperature of resistive midpoint.

Yb_xY_(1-x)Ba_2Cu_3O_(7-y)的超导载流特性

本文系统地研究了Yb_xY_1 _xBa_2Cu_3O_7-y)系统的微结构、超导临界温度以及超导载流特性。发现:随着Yb含量的增大,样品的超导临界温度没有很大变化,但晶粒度逐渐减小,超导临界电流密度系统地下降。作者认为:在这种弱连接颗粒超导体中,细化晶粒无助于提高其临界电流密度。

Y—Ba—Cu—Al—O体系的X射线光电子能谱研究

对单相样品YBa_2Cu_3 _xAl_xO_(7-y)进行了X射线光电子能谱(XPS)、O缺位以及电阻-温度关系的测量。结果发现,Al在1-2-3相中有可能部分地替代了Cu和Y的位置。由于Al^(3+)的存在,使得含量增加,0的环境趋于一致,XPS图谱上O_(15)两个状态的区别很不明显。而明显地观祭到了Cu^(3+)的存在。

金属玻璃Zr_(78)Co_(22)中的弱局域化效应

测量了超导金属玻璃Zr_(98)Co_(22)的磁阻和上临界磁场H_(c2)。磁阻的实验结果定性地与包含自旋-轨道散射的三维弱局域化理论相符,而定量则有明显的偏差,其偏差主要来源于超导涨落效应。在所测量的温区内,上临界磁场H_(c2)随温度呈线性变化,同时还得出超导金属玻璃Zr_(78)Co_(22)中的非弹性散射主要来源于电子-声子相互作用,其散射几率τ_i^(-1)=1.3×1O^(10)T^2,略小于Bergmann理论所预言的值。

HIGH T_c SUPERCONDUCTIVITY IN THE SINGLE-PHASE Ba_2HoCu_3O_(7-δ)

In the current researching for high Tc superconductors, the most intensive attention has been paid to the system La（Y）-Ba（Sr）-Cu（O）. Now it has been identified that the superconducting phase in Ba（Sr）-La-Cu-O system belongs to the K2NiF4-type