Compositional tuning and phase homogeneity in hexaferrite–spinel (1-x) BSFO-xNCFO nanocomposites: A comparative synthesis approach

This study examines the effect of different synthetic techniques on the structural, microstructural, vibrational, and magnetic characteristics of (1 − x)Ba₀.₅Sr₀.₅Fe₁₂O₁₉ + xNi₀.₅Co₀.₅Fe₂O₄ [(1 − x)BSFO–xNCFO] composites with x = 0, 0.25, 0.5, 0.75, and 1 synthesized via solid-state and sol-gel methods. XRD results verified that there was no presence of any impurity phase in the hexagonal BSFO and cubic NCFO formation. The solid-state samples had higher crystallite sizes (51.6 – 109.8 nm) than sol-gel samples (25.7 – 32.2 nm), while SEM results showed that the grains were larger in size (93 – 124.5 nm) than sol-gel grains (13 – 25 nm). Williamson-Hall analysis suggested that there was tensile strain in BSFO-rich samples and compressive strain in NCFO-rich samples. EDS confirmed the expected elemental composition and high chemical purity, while elemental mapping of the x = 0.5 samples showed broad spatial distribution of the constituent elements for both synthesis routes. FTIR and Raman spectra confirmed the hexaferrite-to-spinel structural transition. All the samples displayed ferrimagnetic properties. Solid state samples possessed saturation magnetization of 64–67 emu g⁻¹ , while sol-gel samples had saturation magnetization of 18–54 emu g⁻¹ . Coercivity varied from 710 to 65 Oe and 883–215 Oe with increased NCFO amount. In general, solid-state method was beneficial for crystallinity and magnetization, while sol-gel method produced finer nanostructures.