Akademik Veri Yönetim Sistemi
Materials Chemistry and Physics, cilt.350, 2026 (SCI-Expanded, Scopus)
The lanthanum (La3+) doped Ni–Mn based nanospinel ferrites, Mn0·5Ni0.5LaxFe2-xO4 (x ≤ 0.1) NSFs, were synthesized by sol gel auto-combustion method. In XRD patterns, the presence of high intense (311) diffraction peak, confirmed that all samples are spinel ferrites. According to Scherer method, DXRD (crystallite size) of the products are within the range 10–15 nm. Further, the calculated crystallite size was correlated with Williams's Hall, modified Scherrer and size strain plot (SSP) method. The cubic morphology and chemical composition of samples have been verified by SEM, TEM, HR-TEM and EDX. The electrical and dielectric properties were characterized using impedance spectroscopy over a range of temperatures and frequencies. The analysis of AC and DC conductivity revealed a thermally activated, non-monotonic conduction mechanism dependent on the La3+ doping level. To deconvolve the contributions from bulk and interfacial regions, impedance data was fitted to an equivalent circuit model, allowing for the separation of grain (Rg) and grain boundary (Rgb) resistances4. The corresponding activation energies for grain (Ea,g) and grain boundary (Ea,gb) conduction were determined from Arrhenius plots. The results demonstrate a complex interplay of competing mechanisms: at low doping levels (x ≤ 0.06), La3+-driven charge compensation (i.e., partial reduction of Fe3+ to Fe3+) enhances small-polaron hopping, facilitating carrier transport and reducing the activation energy. Conversely, at higher concentrations (x ≥ 0.08), the segregation of large La3+ ions at intergranular regions leads to the formation of insulating secondary phases, which create significant barriers to charge migration and sharply increase the activation energy. An optimal composition was identified at x = 0.06, which exhibited the minimum activation energies for both grain (Ea,g = 256 meV) and grain boundary (Ea,gb = 303 meV) conduction. The dielectric properties were governed by Maxwell-Wagner interfacial polarization, with the x = 0.06 sample showing the most favorable balance of properties. This work demonstrates that La3+ substitution is an effective method for tuning the electrical and dielectric response of Mn–Ni ferrites by modulating the balance between intragrain charge transport and intergranular barrier effects.