Impact of La–Bi co-substitution on the structural, morphological, and dielectric properties of SrFe12O19: a comprehensive study

This research investigates sol–gel auto-combustion synthesized Sr_1-xLa_xFe_12-yBi_yO₁₉ (x = 0–0.25, y = 0–0.5) nanoparticles, focusing on La³⁺ and Bi³⁺ co-substitution effects on structural and dielectric properties. X-ray diffraction confirms a single-phase M-type hexagonal ferrite structure (space group P6₃/mmc) with crystallite sizes decreasing from 20 to 13 nm and lattice parameters increasing from 682.08 to 704.73 Å upon La³⁺ and Bi³⁺ co-substitution. Field-emission scanning electron microscopy analysis reveals that the La/Bi substitution results in changes to the morphology and particle size of the samples. Dielectric properties analyzed using impedance spectroscopy reveal a decreased real part of dielectric permittivity with increasing frequency and co-substitution, attributable to interfacial polarization and microstructural changes. The imaginary parts of the electrical modulus diagram exhibit a relaxation peak shift towards lower frequencies with co-substitution, indicating enhanced charge carrier mobility and Debye dielectric response. Findings offer comprehensive insights for tailoring properties in energy storage devices, electronic components, and related fields.