Electrical transport & dielectric properties of hard/soft CoFe2O4@NiAlxFe2-xO4 (x ≤ 0.20) nanocomposites
Nano-Structures and Nano-Objects, vol.46, 2026 (Scopus)
- Publication Type: Article / Article
- Volume: 46
- Publication Date: 2026
- Doi Number: 10.1016/j.nanoso.2026.101700
- Journal Name: Nano-Structures and Nano-Objects
- Journal Indexes: Scopus
- Keywords: Cole-cole plots, Electrical/dielectric properties, Hard/soft nanocomposites, Nyquist plots, Spinel ferrite nanocomposites
- Istanbul Gelisim University Affiliated: Yes
Abstract
Hard/soft CoFe2O4@NiAlxFe2-xO4 (0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.15, 0.20) nanocomposites (H/S CFO@Al→NFO (x ≤ 0.20) NCs) were produced via Sol gel route. The structural, morphological and composition analyses were carried out using XRD, TEM, HR-TEM, SEM along with EDX respectively and the electrical/dielectric features are elucidated in the light of these results. The dielectric and electrical features of products were systematically studied to understand how Al³⁺ ion substitution affects charge transport, polarization mechanisms, and relaxation dynamics. It is evident that AC conductivity (σAC) displayed strong dependence on frequency ( f ) and temperature ( T) , aligning with thermally activated small-polaron hopping. It was found that moderate levels of substitution (say, x = 0.02 – 0.06) increased conductivity due to cation redistribution and local structural distortion, while higher substitution levels (x ≥ 0.08) decreased σAC due to dilution of Fe²⁺/Fe³⁺ hopping centers. It is interesting that DC conductivity (σDC) tracked Arrhenius behavior, with activation energy ( E A ) rising to about 406 meV for 0.08 ≤ x ≤ 0.15, then sharply dropping to 267 meV at x = 0.20, indicating structural relaxation and the reopening of alternative conduction pathways. Dielectric constant (εr′) and loss (εr″) both showed significant dispersion influenced by Maxwell–Wagner (M-W) polarization and thermally activated hopping process, with Al³⁺ ion substitution notably affecting interfacial polarization strength. Furthermore, both impedance spectroscopy and electric modulus confirmed non-Debye relaxation, with T -driven shifts towards higher frequencies and substitution-driven evolution from grain-boundary-dominated to grain-controlled conduction.