Temperature-dependent electrical conductivity and dielectric response of Co-doped MnFe2O4spinel ferrite
摘要
This study examines the frequency-dependent transport properties of cobalt-doped manganese ferrite samples synthesised via a rapid auto-combustion method across a temperature range. It is observed that the average crystallite dimension using the Debye–Scherrer and Williamson-Hall method ranges from 36 to 56 nm, and the lattice constant varies between 8.23 and 8.33 Å with an increase in Co2+ concentration. While the calculated X-ray density ranged from 5.31 to 5.49 g/cm3, the strain and dislocation density varied from 3 × 1014 to 7 × 1014 m−2; a cubic spinel structure was confirmed through X-ray diffraction analysis. The electrical properties were studied from 100 Hz to 1 MHz and 303 to 453 K. The Mn-Co ferrite (MC) nanoparticles showed frequency-dependent, relaxation-type dielectric behaviour and thermally activated traits, confirming their semiconductor nature. The AC conductivity’s frequency dependence follows Jonscher’s power law, and an Arrhenius plot is used to determine the activation energy (0.25 − 0.35 eV). The relaxation time was around 10−6–10−7 s, indicating a thermally activated polaron hopping mechanism. Dielectric analysis indicated that charge carrier hopping is the primary conduction mechanism, aligning with Maxwell–Wagner’s and Koops theories, as confirmed by impedance and Nyquist plot analysis. Among the MC samples, MC-2 (x = 0.3) exhibits superior dielectric performance and conductivity (1.15 × 10−3) due to an efficient charge transport mechanism influenced by mixed valence states and polaron hopping. The enhanced electrical conductivity is attributed to the conversion of Co2+ and Mn2+ into Co3+ and Mn3+, respectively, at the A and B sites. Furthermore, its decreased impedance at higher temperatures makes it a promising option. The MC nanoparticle can be utilised in sensors, energy storage systems, and high-frequency electromagnetic components.