Exploration of electrical and dielectric properties of Ho-substituted SrBa-hexaferrite/Ni-spinel ferrite nanocomposites

Hard/soft Sr_0.5Ba_0.5Ho_xFe_12−xO₁₉/NiFe₂O₄ nanocomposites (H/S Ho-SBF/NFO (x ≤ 0.08) NCs) have been synthesized via a one-pot sol–gel combustion route. X-ray powder diffraction analysis confirmed the formation of both cubic and hexagonal structures and nano size of all samples. The chemical compositions of the products were followed via Energy Dispersive X-ray spectroscopy (EDX). This study systematically explores the dielectric and electrical properties of H/S Ho-SBF/NFO (x ≤ 0.08) NCs, where the Ho³⁺ ion doping ranges from 0.00 to 0.08. Measurements encompassed up to 3.0 MHz and between 20 and 120 °C. The investigation includes an in-depth analysis of ac/dc conductivity, dielectric constant, dielectric loss, dissipation factor, and real and imaginary modulus (ImM) across the entire range of Ho³⁺ ion substitution ratios. Results demonstrate that conductivity variations exhibit power law dynamics relative to frequency (f), predominantly influenced by Ho³⁺ ion substitutions in the NCs. The f-dependent behavior of the dielectric constant across all NCs underscores its sensitivity to the substitution ratio “x”, with most dielectric parameters attributed to interactions between grains and grain boundaries. These findings align with conduction mechanisms typical in compositional ferrites, consistent with Koop’s model.