Analysis of electro-active regions and conductivity of BaMnO3 ceramic by impedance spectroscopy

Polycrystalline BaMnO3 ceramic powders were prepared using the conventional mixed oxide route accompanied with several milling processes. Single phase formation was verified by recording the X-ray diffraction pattern of the powder as well as sintered pellet at room temperature. Scanning electron micrograph and energy dispersive X-ray spectrum of cross-sectional view have shown that sintered pellet is highly porous and contains only Ba, Mn and O elements, respectively. Analysis of impedance spectroscopy was carried out via the complex impedance and complex modulus formalisms. These results have shown that BaMnO3 behave as semiconducting material. Furthermore, as a consequence of electrically inhomogeneous nature of the sample, it was observed that the electroactive regions (such as grain, grain boundary and sample-electrode interface) are overlapped in the applied frequency domain with dominant grain boundary effect. An equivalent circuit model (R (g) C (g))(R (gb) Q (gb))(R (e) Q (e)) was employed to fit the temperature dependent impedance spectroscopy data. Study of grain and grain boundary conductivities suggest that grains are more conductive than grain boundaries and conduction mechanism followed correlated barrier hopping (CBH) model.