Dielectric Relaxation and Electrical Transport Mechanism of NiFe2O4/MnPrxFe2−xO4 (x≤0.10) Nanocomposites

Abstract

In this study, the dielectric relaxation and electrical transport mechanism of MnPrxFe2−xO4/NiFe2O4 (x ≤ 0.10) nanocomposites (NFO/MnPrxFe2−xO4 (x ≤ 0.10 NCs)) were systematically investigated as a function of the Praseodymium (Pr) substitution ratio (x ≤ 0.10) and temperature (20–120 °C). MFO nanoparticles (NPs), NFO NPs, and NFO/MnPrxFe2−xO4 (x ≤ 0.10) NCs were created via a one-pot sol–gel route. XRD (X-ray powder diffraction) analyses confirmed the purity of MFO NPs, NFO NPs, and NFO/MnPrxFe2−xO4 (x ≤ 0.10) NCs (with the presence minor amount of α-Fe2O3 for x = 0.08 and 0.1). The DXRD (crystallite size) of NCs was estimated between 24 and 57 nm. The characterization was performed using impedance spectroscopy and the electric modulus formalism to deconvolve the contributions from grain and grain boundary effects. All NCs exhibited semiconductor-like behavior with a negative temperature coefficient of resistance (NTCR), governed by a thermally activated hopping mechanism. A non-monotonic dependence of dc resistance on the substitution ratio was observed, with a minimum value, corresponding to maximum conductivity, identified at x = 0.06. Conversely, electric modulus analysis revealed that the bulk (grain) dielectric structure becomes maximally complex at x = 0.04, characterized by the emergence of multiple, well-resolved relaxation mechanisms. This differential influence of the dopant on the grain and grain boundary properties highlights a pathway for selectively engineering the overall conductivity and internal dielectric response of ferrite-based nanostructures for targeted electronic applications.