Conductivity behavior and impedance studies in BaTiO3-CoFe2O4 magnetoelectric composites

Two phase magneto-dielectric composite of Barium titanate and Cobalt ferrite (BT-CFO) has been prepared via solid state reaction technique. The structure has been investigated by Raman spectroscopy and confirms the presence of composite phase. Electrical properties of BT-CFO composites were studied thoroughly in 100 Hz to 1 MHz frequency range and in 50 degrees C-450 degrees C temperature range. The dielectric measurements reveal Maxwell-Wagner polarization and thermal activated relaxation process arising from movement of defects and ions in BT and BT-CFO composites. Particularly BT-5CFO composite exhibited a surprising low dielectric loss approximate to 0.3 over the frequency range of 100 Hz-1MHz and promises industrial application. The thermal variation of Impedance parameters reveals the resistive nature of the composites and the presence of two thermally activated relaxation mechanism present in BT and BT-CFO composites. The modulus studies confirm the non-Debye type relaxation processes prevalent in BT-CFO composites. The electrical conduction mechanism occurs through over-lapping large polaron tunneling (OLPT) in BT and through non-overlapping small polaron tunneling (NSPT) at low temperatures to correlated barrier hopping (CBH) at high temperatures in BT-CFO composites. The addition of CFO in BT localizes the polarons and enhances the conductivity. The magneto-dielectric coupling effect (% MD) is found to have a maximum value of 1.2 in magnitude at 7 kOe for BT-5CFO composite and increases with the amount of CFO in BT-CFO composite. These results could be beneficial in enhancing the properties of BT-CFO based systems.