Nd_(1-x)Sr_xMnO_3中掺杂浓度对电脉冲诱导电阻转变效应的影响

Effect of doping concentration on electric-pulse-induced resistance in Nd_(1-x)Sr_xMnO_3 ceramics

采用两线测量模式对固相烧结方法制备的Nd_(1-x)A_xMnO_3(A=Ba,Ca,Sr,x=0—0.9)陶瓷样品电脉冲诱导电阻转变(EPIR)效应和Ⅰ-V特性进行了测量.结果表明,与Nd_(0.7)Sr_(0.3)MnO_3一样,相同浓度掺杂的Nd_(0.7)Ba_(0.3)MnO_3和Nd_(0.7)Ca_(0.3)MnO_3样品也能诱发稳定的室温EPIR效应.进一步对Nd_(1-x)Sr_xMnO_3系列样品的EPIR研究表明,这种界面相关的EPIR效应与样品中电子或空穴掺杂浓度密切相关,在半掺杂(x=0.5)附近,样品与电极接触界面能诱发稳定的EPIR效应.然而,随掺杂浓度的进一步增大或降低,EPIR效应逐渐出现减弱、不明显到完全消失的过程.产生这种现象的原因可能与锰氧化物中由于掺杂浓度差异所导致的界面缺陷在不同极性脉冲激励下重新分布而产生的内电场强弱有关.

Electric-pulse-induced resistances（EPIRs） andⅠ-Ⅴ characteristics of polycrystalline Nd_（1-x）A_xMnO_3（A = Ca,Ba,Sr,x = 0-0.9） ceramics synthesized by solid state reaction are investigated.The results show that similar to Nd_（0.7）Sr_（0.3）MnO_3,compounds Nd_（0.7）Sr_（0.3）MnO_3 and Nd_（0.7）Sr_（0.3）MnO_3,with the same doped concentration as that of Nd_（0.7）Sr_（0.3）MnO_3,each can also exhibit a nonlinearⅠ-Ⅴbehaviour and a stable EPIR effect at room temperature.Further studies on the Nd_（1-x）A_xMnO_3 series indicate that the stability of EPIR is closely correlated with the Sr doped concentration.Around the half doping x = 0.5,the EPIR effect can be observed stably.With Sr concentration increasing or decreasing,however,the EPIR becomes weaker gradually and disappears completely if Sr concentration further increases or decreases.The redistribution of various defects between the electrode and bulk interface with polar pulses is proposed to explain the unique transport behaviour.