Temperature induced delocalization of charge carriers and metallic phase in Co0.6Sn0.4Fe2O4 nanoparticles

Abstract

Thermally induced semiconductor to metal transition has been investigated for tin doped cobalt ferrite nanoparticles using impedance spectroscopy in a wide frequency range (100 Hz-2 MHz) from 300 K to 400 K. In addition dc measurements are carried out in temperature range from 285 K to 410 K. Temperature dependence of impedance spectroscopy and dc resistivity reveal semiconductor to metal transition around 360 K. Metallic nature of the system above 360 K has been attributed to dominancy of delocalized charge carriers Fe3+–Fe2+/Co3+–Co2+ interactions over localized charge carriers Fe3–O2−–Fe3+/Co2+–O2−–Co2+ interactions. Interesting temperature dependent electrical behavior of the grain boundaries is reported and has been discussed in term of depletion space-charge layer in the vicinity of grain boundaries.