Influence of sintering temperature and oxygen stoichiometry on electrical transport properties of La0.67Na0.33MnO3 manganite

With a view to investigate the influence of sintering temperature and oxygen stoichiometry on electrical and magnetic properties of sodium-doped lanthanum manganite sintered at different temperatures, a series of samples were prepared by the sol–gel route. The samples were characterized by the XRD studies and the data were analyzed using the Rietveld refinement technique and it has been observed that the materials are having rhombohedral structure with R3¯c space group. The electrical resistivity and thermoelectric power studies were investigated both as a function of crystallite size and oxygen content. To understand the conduction mechanism, the electrical resistivity data have been analyzed and it has been concluded that the variation of electrical resistivity in the ferromagnetic region can be explained by electron–electron scattering process (∼T2) and two magnon scattering processes, while that in the paramagnetic region is explained by the small polaron hopping mechanism. Similarly, the variation of thermopower in the ferromagnetic region is explained on the basis of electron–magnon scattering.