Soft/hard ferrite nanocomposites: Evaluation of temperature dependent dielectric properties

Abstract

Nanocomposites of cobalt ferrite (CoFe2O4) and strontium ferrite (SrFe12O19) were synthesized with various weight ratios 1:1, 1:2, 1:4, 1:8 and 1:16, by chemical co-precipitation route with higher content corresponding to SrFe12O19. Dual phase refinement employed for the prepared composites and confirms the presence of independent CoFe2O4 and SrFe12O19 phases. The increasing weight fraction of SrFe12O19 in the prepared composites is in accordance with its increasing weight ratio. An increase in compressive strain in the composites was attributed to larger ionic radius of Sr+2 ions. The electrical behavior in the composites was described by Cole-Cole plots at 250 °C from 20 Hz-106 Hz. An increase in impedance with increasing weight ratio of SrFe12O19 was observed, due to creation of effective scattering centers. Conductivity mechanism was explained by Overlapping large polaron tunneling (OLPT) model. A decrease in dielectric constant with increasing frequency is due to decreasing space charge polarization, due to inability of charge carriers to follow the varying ac field. Decreasing trend in dielectric loss for the prepared composites confirms their utility in microwave absorption applications.