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Dielectric and optical properties of FeCoNbO (x=0 and 0.10) ceramics
Authors: Jucá, RF; Benali, EM; Pina, J.; Graca, MPF; Saraiva, GD; Silva, EJCDE; Costa, BFO
Ref.: J. Electroceramics Early Access (2026)
Abstract: The dielectric and optical properties of Fe1-xCoxNbO4 (x = 0 and 0.10) ceramics were investigated by impedance spectroscopy, electric modulus analysis, and diffuse reflectance measurements. The electrical response reveals thermally activated relaxation processes associated with grain and grain-boundary contributions, dominated by hopping conduction mediated by oxygen vacancies and localized mixed-valence states. Activation energies in the range of 0.52-0.74 eV were obtained from Arrhenius analysis. Cobalt substitution leads to higher impedance values and an enhanced dielectric constant, indicating modifications in lattice structure and defect distribution. Optical measurements exhibit strong UV-visible absorption for both compositions, while Co incorporation reduces the absorption intensity and slightly decreases the optical band gap, evidencing changes in the electronic structure and metal-oxygen interactions. These results highlight the role of Co substitution in tuning the dielectric and optical properties of FeNbO4-based ceramics.
