Admittance spectroscopy and complex impedance analysis of Ti-modified La0.7Sr0.3MnO3

Titanium was added to La0.7Sr0.3MnO3 (LSM) to study its effect on electrical conductivity. Samples were characterised by impedance measurements. It was found that conductivity in the reference material without titanium is temperature independent. On the contrary, when Ti is introduced different conduction mechanisms are observed. Electronic conduction is found to be dominated by thermally activated hopping of small polarons at high temperature and variable-range hopping at low temperature. Impedance spectrum analysis shows that the material can be described as a grain and grain boundary medium. The activation energy deduced from analysis of the conductance spectrum matches very well with the value estimated from the relaxation time; then, it is thought that relaxation process and electrical conductivity are attributed to the same defect. (C) 2007 Elsevier B.V. All rights reserved.