Dielectric relaxation and conduction mechanism of cobalt ferrite nanoparticles

•Cobalt ferrite nanoparticles prepared by the auto combustion method.•Dielectric relaxation was explained by impedance spectroscopy.•Interfacial polarization plays important role in cobalt ferrite nanoparticles.•Overlap large polaron tunneling conduction is responsible for ac conductivity.•DC conductivity is mainly due to the small polaron conduction. The electric transport behavior of nano cobalt ferrite was studied in details within frequency window of 100Hz and 1MHz in the range of temperature of 25–200°C. No grain relaxation was observed whereas interfaces (grain boundary and electrode surface contact) became the dominant conduction regions. Both ac and dc conduction mechanism was investigated thoroughly. Overlapping of large polaron tunneling (OLPT) mechanism was found to be responsible for ac conduction process. The value obtained for mobility (10−10cm2/Vs) of charge carriers indicated the possible small polaron hopping for dc conduction process. The dc resistivity data was fitted with Mott and Davis model and the derived parameters confirmed the dc conduction of non-adiabatic nature which was due to small polaron hopping in nano cobalt ferrite.