Electrical transport and dielectric relaxation in hard/soft[SrSe0.1Fe11.9O19]x/[Ni0.5Co0.5Fe2O4]y (x = 1/2, 2/3, 1/1, 3/2 and 2/1) nanocomposites: Composition-dependent AC/DC conductivity and modulus analysis
Nano-Structures and Nano-Objects, cilt.46, 2026 (Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 46
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.nanoso.2026.101629
- Dergi Adı: Nano-Structures and Nano-Objects
- Derginin Tarandığı İndeksler: Scopus
- Anahtar Kelimeler: AC/DC conductivity, Dielectric properties, Hard-soft ferrite nanocomposites, Modulus analysis, Se substitution
- İstanbul Gelişim Üniversitesi Adresli: Evet
Özet
A one-pot green sol–gel route was employed to synthesize [SrSe0.1Fe11.9O19]x/[Ni0.5Co0.5Fe2O4]y nanocomposites ((Se:Sr-HF)x/(NiCo-SF)y NCs) with compositional ratios x/y = 1/2,2/3,1/1,3/2 and 2/1. The XRD (X-ray diffraction), SEM (Scanning electron microscope), TEM (Transmission electron microscope) along with EDX (Energy dispersive X-ray) analyses confirmed the chemical purity and substantial agglomerations of spherical and hexagonal particles and chemical composition of all products respectively. The electrical and dielectric responses of the (Se:Sr-HF)x/(NiCo-SF)y NCs were systematically examined over a wide frequency and temperature range for 0.5≤x/y≤2.0. 3D AC conductivity maps reveal thermally activated, frequency-dependent transport governed by hopping conduction and Maxwell–Wagner interfacial polarization. The composition with x/y = 3/2 exhibits the highest conductivity and the weakest frequency dispersion, indicating the formation of an optimally connected percolative network with reduced interfacial blocking. DC conductivity follows a two-region Arrhenius behavior with a transition near 50 °C, separating a low-temperature defect- or trap-controlled regime from a high-temperature small-polaron hopping mechanism. The lowest high-temperature activation energy (Ea=377 meV) is observed for x/y = 3/2, consistent with its superior charge transport characteristics. Dielectric permittivity and loss analyses demonstrate strong composition-dependent interfacial polarization, with Se:Sr-rich NCs displaying enhanced dispersion and elevated dielectric constants. Impedance and electric modulus spectroscopy further indicate dominant grain-boundary contributions in spinel-rich samples, whereas increasing hexaferrite content intensifies interfacial polarization and introduces multiple relaxation processes. Se ion-substitution acts as an effective electronic modifier by inducing lattice distortion and charge-compensation effects, thereby influencing Fe²⁺/Fe³⁺ hopping dynamics and dielectric relaxation behavior. The impact of Se on electron transport pathways and relaxation behavior is described, with reference to previous studies on Se-doped ferrites. Inclusively, precise tuning of the (Se:Sr-HF)x/(NiCo-SF)y ratio enables concurrent optimization of carrier density, hopping probability, and interfacial homogeneity, identifying x/y ≈ 3/2 as the most promising composition for high-frequency magnetic and electronic applications.