Electrical transport properties of cobalt-doped MgAl₂O₄ nanoparticles

The electrical transport properties of MgAl_2−xCo_xO₄ (where x = 0.0, 0.5, 1.0, 1.5, 2.0) were investigated at room temperature. The dielectric behavior of the samples, and the contribution of the grains and the grain boundary regions to the electric response of the samples were observed using impedance spectroscopy in the frequency range of 20 Hz to 2 MHz. The DC conduction behavior was studied by measuring current density J against electric field E. It was observed that the grains and grain boundaries both contribute equally to the variation in electric response caused by changing the dopant concentration of cobalt in MgAl₂O₄. The combined Z″ and M″ spectroscopic plots indicated the presence of small polaron hopping conduction in the grain region of the samples. Moreover, the 25% doped sample showed minimum conductivity among all samples, which was two orders of magnitude less than that of the pure sample. (paper)