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

Oxygen deficient tetragonal phases of SrFe1−xTixO3−δ (x > 0–0.3) show semiconducting behavior when compared to the metallic, cubic phase of x = 0 and δ = 0. This study aims at understanding the compositional dependence of ac conductivity as a function of temperature for Ti doped SrFeO3−δ. 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−δ (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.

Graphical abstractObservation of positive temperature coefficient of resistance (PTCR) at atmosphere pressure and moderate temperature in tetragonal 20% Ti doped nano SrFeO3−δ.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Connection of TCR to electrical modulus. ► Observation of PTCR in tetragonal nano SrFexTi1−xO3−δ at ambient pressure. ► Site disorder due to Ti doping and oxygen vacancy explains the conductivity.