Structural properties and electrical behaviour in the polycrystalline lanthanum-deficiency La1-x□xMnO3 manganites

Electrical conductance and X-ray diffraction (XRD) measurements of lanthanum-deficiency La1-x square xMnO3 (x = 0.05, 0.10 and 0.20) polycrystalline samples were performed to examine the effect of the internal pressure at B-site on the conduction mechanism. The structural study reveals that all samples crystallize in the rhombohedral system. The electronic conduction appears to be thermally activated at high temperature, which indicates the presence of semiconductor behaviour. The increase of the x content converts 3x Mn3+ to 3x Mn4+ ions with smaller ionic radius, which reduces the internal pressure and leads to the increase of the one-electron bandwidth W. This increase causes the appearance of metallic behaviour at low temperature for x 0.10 and 0.20 content. (C) 2009 Elsevier B.V. All rights reserved.