Abstract
The transport properties of Ga-doped La-0.7(Ba, Sr)(0).3Mn1-xGaxO3 (x=0.0, 0.1 and 0.2) perovskite materials were investigated by admittance spectroscopy over a wide range of temperatures and frequencies. The electronic conduction was found to be dominated by thermally activated hopping and to depend strongly on Ga-content. Results have shown samples with x=0.0 and 0.1 exhibit a metallic behavior at low temperature and a semiconducting one at high temperature. The temperature (T-MI) of the metal insulator transition was found to be about 180 and 120 K for samples with x=0.0 and 0.1, respectively. Ga doping leads to a depletion in the number of hopping electrons, which suppresses metallicity and pushes the system in semiconductor side. Besides, the activation energy (Ea) deduced from the variation of conductance as a function of temperature, was found to increase from 89 to 165 meV when x increased from 0.0 to 0.2. This increase can be explained by the decrease of charge carriers with increasing Ga-content. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.