Resistivity and Susceptibility of Y-Ba-Cu and Bi-Sr-Ca-Cu Oxides

The resistivity and magnetic susceptibility ofthe quenched samples for the Y-Ba-Cu oxideswere measured at room temperature.Themeasurement for the temperature dependence of theamorphous Bi-Sr-Ca-Cu oxides with differentheat treatment temperature was made.Theresistivity and the parameters C in the formulax=X_0+C/(T-0)of the quenched samples forY-Ba-Cu oxides decreased with lowering quenchtemperature,and their susceptibility did not varymonotonously with quench temperature.The tem-perature dependence of the amorphousBi-Sr-Ca-Cu oxides gradually deviates fromCurie-Weiss law with increasing heat treatmenttemperature.The local magnetic moments forY-Ba-Cu and amorphous Bi-Sr-Ca-Cu oxidesgradually decrease with decreasing quench tempera-ture or increasing heat treatment temperature.     

EFFECT OF OXYGEN CONTENT ON STRUCTURAL DISTORTION AND SUPERCONDUCTIVITY OF Y-Ba-Cu-O SYSTEM

<正> 最近,我们在Y-Ba-Cu氧化物中获得T_C高于90K的超导电性.Beyers等认为在此种化合物体系中起超导作用的相具有正交层状钙钛矿型相结构,并称之为超导相.进一步的工作发现,在Y-Ba-Cu氧化物中,同一成分的试样     

Bi—Sr—Ca—Cu—O系氧化物熔体的凝固产物及其向超导体的转变

用不同的熔化方法和后续热处理制备了BSCCO系超导体,研究了冷却速度、退火温度、退火时间和不同熔化方法对相变的影响,运用X射线衍射,光学显微镜,电子探针,差热分析,热重分析,导电性和抗磁性测量等分析了组织、结构和性能,结果表明,名义成分为Bi_2(Sr,Ca)_3Cu_2O_x的熔体在空气中凝固时,Bi_2(Sr,Ca)_3Cu_2O_(8+δ)(简称2212)超导相是较稳定的相;包含Bi_2(Sr,Ca)_2CuO_(6+δ)(简称2201)相的产物是易生成的亚稳相;在急冷条件下生成非晶后两者通过后续热处理可以转变成2212相,最佳退火温度在780-870℃间,非晶相也可转变成2201相,激光浮区熔化法(LFZM)制成的2201相退火后易转变成片状或纤维状的2212相,有利于改善超导相颗粒间的连接,提高临界电流密度     

（Fe_（0．99）Mo_（0．01））_（78）Si_9B_（13）非晶合金的低温韧脆性研究

用ＤＳＣ，ＳＥＭ，Ｃｕｒｉｅ温度和电阻测量等多种实验手段研究了非晶条带（Ｆｅ_（０．９９）Ｍｏ_（０．０１））_（７８）Ｓｉ_９Ｂ_（１３）的低温退火脆性．发现其特征脆化温度约为２４４℃，产生了一个有序度增加的结构弛豫过程．同时，伴随有纳米颗位α－Ｆｅ（Ｓｉ，Ｍｏ）多晶组织从非晶基体中析出．进一步提高退火温度，则由于新的有序原子团的出现，自由体积等可动单元再次增大，从而释放应力，恢复韧性．