Dielectric, Complex Impedance, and Electrical Transport Properties of Erbium (Er3+) Ion-Substituted Nanocrystalline, Cobalt-Rich Ferrite (Co1.1Fe1.9-xErxO4)

Erbium (Er3+) substituted nanocrystalline, cobalt-rich ferrites, which can be represented chemically as Co1.1Fe1.9-xErxO4 (CFEO; x = 0.0-0.2), were synthesized by the sol-gel autocombustion method. The structural, dielectric, and electrical transport properties of CFEO were investigated in detail. CFEO materials crystallize in a spinel cubic structure for x <= 0.10; formation of orthoferrite (ErFeO3) secondary phase was noted for x >= 0.15. Microstructural and compositional studies revealed the formation of spherical, elongated grains with stoichiometric presence of Co, Fe, Er, and O. The dielectric constant (epsilon') dispersion fits to the Debye's function for all CFEO ceramics. The relaxation time and spread factor obtained from epsilon' dispersion are similar to 1.0(-3)s and similar to 0.50 (+/- 0.10), respectively. The complex impedance analyses confirm a grain-interior mechanism contributing to the dielectric properties. Semiconducting behavior and small polaron conduction mechanism were evident in electrical transport properties of CFEO materials.