Study on the structural, optical, vibrational and dielectric properties of Cr2+-doped SnFe2O4 spinel ferrites

Abstract

Herein, we have examined the effects of Cr²⁺ doping on the structural, optical, microstructural, and dielectric properties of SnFe₂O₄ spinel ferrites prepared by the conventional solid-state route. X-ray diffractometry (XRD) analysis confirmed the formation of a single-phase cubic spinel structure with the space group Pn. A decrease in the lattice parameters and crystallite size was observed with increasing Cr²⁺ content. Scanning electron microscopy (SEM) revealed a homogeneous and densely packed microstructure with a reduced grain size upon Cr²⁺ doping. The optical band gap energies, as measured by UV-vis spectrometry, were observed to decrease from 2.58 eV to 2.32 eV. Fourier transform infrared (FTIR) spectrometry revealed subtle modifications in the metal–oxygen (M–O) vibrational bands due to Cr²⁺ doping. Frequency and concentration (x) also significantly influenced the dielectric properties of the synthesized samples. An improved resistive grain boundary behavior and less space charge polarization were indicated by a significant decrease in tan δ and an improvement in frequency stability, respectively, as the concentration of Cr²⁺ increased. With increasing Cr²⁺ content, a decrease in σ_ac was observed, which in turn reduced both the leakage current and tangent loss. The observed reduction in modulus due to doping reflects enhanced charge transport and diminished polarization, making the material suitable for use in memory devices, sensors, and spintronic components.