Non-universal dielectric relaxation in SrFeO3 − δ

SrFeO3 − δ compound is prepared by the thermal decomposition method followed by ball milling. Analysis of Mössbauer spectrum and X-ray diffraction study proves the presence of multi-phase nature, i.e., Sr8Fe8O23 and Sr4Fe4O11 phases at room temperature. Furthermore, the Mössbauer spectrum at room temperature evidenced the presence of major Fe3.5+ which is the resultant of equal contributions of Fe4+ and Fe3+. The Nyquist plot at all measured temperatures (80-230 K) suggests that the dielectric response is well associated with single relaxation time (exponential parameter, n∼1) i.e., the Debye-type. Modulus analysis exhibits the non-universal dielectric behaviour (stretched exponential parameter, β>1) below 230 K and the Debye-type responds (β∼1) at and above 230 K. The Debye-type behaviour exhibited by SrFeO2.81 at around room temperature in its defect state offers a new opening for this material for multifunctional applications.