[en] In this work, we report structural, thermal, optical and electrical properties of chemically synthesized (unmilled) and mechanically milled nano-powder. Prepared samples were characterized by XRD, TGA-DSC, FTIR and TEM. Rietveld refinement of X-ray diffraction was employed for microstructural analysis and it confirmed successful synthesis of pure, single phased tetragonal with space group 141/amd. Chemical bonds and functional groups of the samples were confirmed by FTIR. TGA-DSC curve confirms long range temperature stability of the sample. Impedance spectroscopy analysis reveals the fact that resistance decreases with temperature and for the milled sample, conductivity is quite higher than the unmilled sample at a certain temperature. Master curve of Z” shows good scaling behaviour of the sample with temperature and frequency. DC conductivity was found to be thermally activated and AC conductivity obeys universal Almond West equation. Temperature and frequency dependent dielectric behaviour is also explained. Attempt was made to correlate electrical properties with variation of grain size and microstrain of the unmilled and milled powder. Such low-cost and easily synthesised non-volatile cobalt magnetite nano-powder with high temperature stability and effective electrical properties makes it suitable as electrolyte material in Solid Oxide Fuel Cell (SOFC). (author)