采用热压法获得了具有不同混合比例的超导氧化物La1.85Sr0.15CuO4/超高分子量聚乙烯导电复合材料,并利用x射线衍射、扫描电子显微镜和标准四引线方法对复合材料的结构和低温电输运性质进行测量.实验结果显示,超导氧化物La1.85Sr0.15CuO4颗粒随机分布在聚合物本体中,相互间没有连接构成网络结构.在正常态下,复合材料的电阻-温度变化曲线给出类半导体行为.但对应于超导氧化物La1.85Sr0.15CuO4的超导转变温度Tc处,复合材料的电阻-温度变化曲线出现了极小值.室温下电阻率ρ随外加电场强度E的变化曲线测量结果表明,ρ-E曲线为一线形关系,随着电场强度E增加,电阻率ρ下降.文中对可能存在的导电机制进行分析,结果表明隧道贯穿模型可以很好地解释复合材料的导电机制.另外,外加电场强度E对复合材料的电输运特性有明显的影响.
The composites of the ultra high molecular weight polyethylene and La1.85Sr0.15CuO4 superconductor with different mixture ratios have been prepared by pressure sintering. The temperature dependence of the resistivity of the conductive composites has been measured. It is found that the composites with the random dispersions of conductive particles in the polymer matrix show a semiconductor-like resistivity behavior in normal state. However, there is a minimum in the ρ-T curve of the composites corresponding to the Tc of La1.85Sr0.15CuO4. The ρ-E curve of the composites was also measured at room temperature, which gives a linear relationship. The possible conduction mechanics has been discussed.
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