Nd0.7Sr0.3MnO3陶瓷EPIR效应的起源

The origin of EPIR effect in Nd_(0.7)Sr_(0.3)MnO_3 ceramics

用两线法和四线法对球磨合成后热处理的Nd0.7Sr0.3MnO3陶瓷样品的电脉冲诱导电阻转变(EPIR)效应进行了测试.结果表明:在Nd0.7Sr0.3MnO3块体中用四线法测得的I-V曲线为非线性,说明Nd0.7Sr0.3MnO3样品在晶(相)界处存在空间电荷层和界面电阻.但用四线法测量EPIR效应时,没有EPIR效应发生,表明晶(相)界处的空间电荷层和肖特基势垒不能产生EPIR效应;对同一样品采用直流两线法测量,其I-V曲线也为非线性,但却发生明显的EPIR效应.说明在Nd0.7Sr0.3MnO3陶瓷中发现的EPIR效应起源于样品与电极之间的接触界面,块体内的晶(相)界处虽能产生相似I-V特性,但却不能发生EPIR效应.

Polycrystalline ceramic Nd0.7Sr0.3MnO3 is synthesized using high-energy ball milling and post heat treatment method.The properties of electric transport are measured using direct current （DC） 4-wire and 2-wire methods.The results show that both the grain （phase） boundary and the electrode-bulk contact interface has interfacial resistance and space charge layer.The two kinds of space charge regions have greatly different effects on the DC transport：for the former,the I-V curve exhibits nonlinear characteristic and no EPIR effect takes place;for the later,however,an obvious EPIR effect is observed even if the I-V curve also shows nonlinear behaviour.It well suggests that for the ceramic Nd0.7Sr0.3MnO3,only the electrode-bulk contact interface can induce the EPIR effect although there is a similar nonlinear I-V characteristic for the grain （phase） boundary and the electrode-bulk contact interface.