Positive temperature coefficient of resistance of tetragonal Ti4+ doped nano SrFeO3-δ

Oxygen deficient tetragonal phases of SrFe1-xTixO3-delta ( x > 0-0.3) show semiconducting behavior when compared to the metallic, cubic phase of x = 0 and delta = 0. This study aims at understanding the compositional dependence of ac conductivity as a function of temperature for Ti doped SrFeO3-delta. Complex impedance spectroscopy data is analyzed based on the Cole-Cole type impedance response functions, and Jonscher's universal power law to explain the dispersive behavior of the electrical conductivity. For the first time, we report a positive temperature coefficient of resistance ( PTCR) behavior in SrFe1-xTixO3-delta ( x = 0.2 and 0.3) at ambient pressure and moderate temperatures. The correlation between PTCR and electrical modulus is investigated. The non-linear variation of the conductivity with increase in Ti doping is attributed to the change in Fe-O bond distances and increase in site disorder. (C) 2013 Elsevier B.V. All rights reserved.