Investigation of Grain, Grain Boundary, and Interface Contributions on the Impedance of Ca₂FeO₅

Abstract

Conductivity properties such as the impedance contributions of grain, grain boundary, and electrode–material interface of brownmillerite-type Ca2Fe2O5 are studied using alternate current (AC) impedance at different temperatures over a wide range of frequencies. The compound was synthesized at 1000 °C by a solid-state reaction. Powder X-ray diffraction confirmed the pure and single-phase formation. The correlation of the electrical properties with the microstructure of the compound was studied by an AC impedance spectroscopic technique at different temperatures (25–300 °C), which demonstrated the contribution of both the grain (bulk) and grain boundary to the impedance. The frequency-dependent electrical conductivity was used to study the conductivity mechanism. The electric impedance and the frequency at different temperatures supported the suggested conduction mechanism.

Keywords

• brownmillerite
• impedance
• grain
• grain boundary and interface