Transport properties of La1−xSrxMnO3 ceramics above metal–insulator transition temperature

Abstract

Single phase Sr-doped lanthanum manganite (La1−xSrxMnO3, 0≤x≤0.4) ceramics have been prepared to study the transport property and conduction mechanism in these materials above the metal–insulator transition temperature (Tp). The measurement of resistivity showed that the conductivity increased with the increasing of Sr concentration. The samples with 0.1≤x≤0.3 exhibited Tp between 258 and 281K, depending on x. We then fitted the resistivity data in the semiconducting region (T>Tp) to check the possible conduction mechanism through two models, i.e., small polaron hopping (SPH) and variable range hopping (VRH). It was found that the transport mechanism in the higher temperature region above θD/2 (θD is Debye temperature) was dominated by the SPH model. But for the lower temperature region (between Tp and θD/2), the conductivity data could be well fitted to the VRH model, where some fundamental parameters (hopping energy Eh and hopping distance Rh) estimated from Mott's relation also obeyed the VRH mechanism. The doping of Sr in the samples caused the reducing of the localization of charge carriers, which thereby led to a decreasing in Eh and Rh.