Improved electrical and dielectric properties of La-doped Co ferrite

We report on the enhanced dielectric constant and electrical resistivity of the Co-ferrite (CoO center dot Fe2O3) by partially substituting Fe with La. Structural characteristics of La-doped Co ferrite namely CoO center dot Fe1.925La0.075O3 indicate the cubic inverse spinel phase with a small amount of LaFeO3 additional phase. The lattice parameter obtained is 8.401 angstrom (+/- 0.001 angstrom which is higher than that reported for Co ferrite (8.387 angstrom +/- 0.001 angstrom The dielectric constant and electrical resistivity of CoO center dot Fe1.925La0.075O3 are higher compared with pure Co ferrite. The dielectric constant dispersion of CoO center dot Fe1.925La0.075O3 in the frequency range of 100 Hz to 1 MHz fits to the modified Debye's function with more than one ion contributing to the relaxation. Temperature-dependent electrical resistivity curves exhibit two distinct regions indicative of two different types of conduction mechanisms. Analysis of the data indicates that the small polaron and variable-range hopping mechanisms are operative in the 220 to 300 K and 160 to 220 K temperature regions, respectively.