Effect of hafnium-incorporation on the microstructure and dielectric properties of cobalt ferrite ceramics

Abstract

Abstract The effect of hafnium (Hf) incorporation on the crystal structure, surface morphology, chemical composition and dielectric properties of cobalt ferrite (CoFe 2 O 4 ) is reported. Hafnium incorporated Co-ferrite (CoFe 2− x Hf x O 4 ) ceramics were prepared by varying the Hf concentration in the range of x =0.0–0.2. X-ray diffraction (XRD) studies indicate that the CoFe 2− x Hf x O 4 ceramics crystallize in inverse spinel change to structure similar to that of pure CoFe 2 O 4 . Hafnium incorporation induces lattice expansion leading to increased lattice constant from 8.374 A for pure CoFe 2 O 4 to 8.391 A for the highest Hf concentration ( x =0.2) in CoFe 2− x Hf x O 4 . Dielectric constant of CoFe 2− x Hf x O 4 ceramics is also enhanced compared to pure CoFe 2 O 4 due to the lattice distortion upon Hf incorporation. Improved dielectric properties of CoFe 2− x Hf x O 4 ceramics compared to pure CoFe 2 O 4 is attributed to the lattice distortion due to larger Hf-ions substituting for smaller Fe-ions associated structural changes with increased Hf concentration. Frequency variation of the dielectric constant shows the dispersion that can be modeled with a modified Debye's function, which considers the possibility of more than one ion, contributing to the relaxation.