Abstract
We have studied the effect of Na substitution on structural, magnetic and electrical properties in La0.67Pb0.33-xNaxMnO3 (0 <= x <= 0.15). All compositions were synthesized using the sol-gel technique. X-ray diffraction and structure refinement show that they crystallize in the rhombohedra structure with the R - 3c space group. All the samples exhibit a paramagnetic (PM)-ferromagnetic (FM) phase transition (T-C) at 363, 328, 305 and 285 K for x = 0, x = 0.05, x = 0.1 and x = 0.15 respectively. The replacement of Pb ion by Na results in a decrease of the metal-semiconductor transition temperature TM-Sc and the magnetoresistance (MR) as well as the resistivity are found to increase. The electrical resistivity in the entire temperature range fit well with the phenomenological percolation theory based on the phase segregation mechanism. (C) 2015 Elsevier B.V. All rights reserved.