Temperature induced delocalization of charge carriers and metallic phase in Co_(0.6)Sn_(0.4)Fe_2O_4 nanoparticles

摘要

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-2MHz) 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 Fe~(3+)-Fe~(2+)/Co~(3+)-Co~(2+) interactions over localized charge carriers Fe~3-O~(2-)-Fe~(3+) /Co~(2+)-O~(2-)-Co~(2+) 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.