Structural, morphological, dielectric, and magnetic properties of CoFe2O4 ceramics at different sintering temperatures

Abstract

Cobalt ferrite (CoFe₂O₄) ceramics were effectively synthesized using the co-precipitation method, followed by an investigation into the impact of sintering temperature on various properties including structure, morphology, magnetism, and dielectric behavior. These obtained ceramics exhibited a spinel ferrite structure with cubic symmetry. The average grain size increased from 0.26 to 0.83 μm, as the sintering temperature raised from 400 to 1000 °C. Dielectric measurements demonstrated significant temperature-dependent behavior across all frequencies, suggesting a pronounced influence on polarization within the ferrites, likely caused by localized electron displacement due to electronic exchange between Fe²⁺ and Fe³⁺ ions along the direction of the applied electric field. Analysis of impedance and modulus confirmed a negative temperature coefficient of resistance (NTCR) response. Additionally, the increase in ac conductivity with temperature was found to enhance charge hopping, resulting in decreased activation energy (E_a) for specimen mobility responsible for conduction. Magnetic properties exhibited enhancement with increasing sintering temperature, with maximum magnetization, coercivity, and remanent magnetization values increasing accordingly. However, non-saturation at high fields suggested surface effects in the CoFe₂O₄ ceramics. Notably, the CFO ceramic sintered at 1000 °C displayed a maximum magnetization value of approximately 74.54 emu/g at room temperature, while the highest coercivity value among all samples was 1368.33 Oe for the sample sintered at 900 °C.