Sintering-Driven Modulation of Lattice Dynamics, Elastic Behavior, and Dielectric Response in Al–Sn Co-Doped Zinc Ferrite Nanoparticles

Abstract

In this work, ZnAl_0.1Sn_0.1Fe_1.8O₄ (ZASFO) ferrites were synthesized via a sol–gel auto-combustion route and sintered at 800°C, 1000°C, and 1200°C to systematically investigate the influence of thermal processing on vibrational, elastic, and dielectric properties. X-ray diffraction confirms the formation of a single-phase cubic spinel structure for all samples. FT-IR analysis reveals characteristic tetrahedral (ν₁) and octahedral (ν₂) metal–oxygen stretching modes, from which site-specific force constants were evaluated. The tetrahedral force constant increases markedly with sintering temperature, indicating enhanced lattice rigidity and improved crystallinity. Elastic moduli derived from IR-based lattice dynamical analysis show increased stiffness, sound velocity, and Debye temperature at higher sintering temperatures, reflecting strengthened metal–oxygen bonding and reduced lattice disorder. Dielectric measurements demonstrate strong frequency dispersion governed by Maxwell–Wagner interfacial polarization and Koop's model, with enhanced dielectric constant and reduced high-frequency loss for samples sintered at higher temperatures. AC conductivity follows Jonscher's universal power law, confirming hopping-dominated charge transport associated with Fe²⁺/Fe³⁺ pairs at octahedral sites. The combined effects of Al³⁺-induced lattice stabilization, Sn⁴⁺-driven charge compensation, and sintering-controlled microstructural evolution establish clear structure–property correlations, highlighting ZASFO ferrites as promising candidates for dielectric and multifunctional energy applications.