Crystallographic modulation and optoelectronic phenomena in NiFe₂O₄/ZrC composites: A multifaceted structural and spectroscopic exploration

This work investigates the structural and optoelectronic properties of nickel ferrite (NFO) composites with varying zirconium carbide (ZrC) content using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, thermogravimetric/differential scanning calorimetry (TGA/DSC), ultraviolet–visible (UV–Vis), and photoluminescence (PL) spectroscopy. XRD confirms a cubic spinel NFO structure with emerging ZrC rock-salt peaks, while crystallite sizes (13–22 nm) and microstrain (10⁻⁵–10⁻³) reveal lattice strain and defect incorporation. FESEM shows morphological evolution from porous NFO aggregates to dense ZrC-rich composites, and elemental mapping affirms homogeneous Ni, Fe, O, Zr, and C distribution. Raman spectra exhibit A_1g phonon modes (600–700 cm⁻¹) alongside ZrC-related bands (200–400 cm⁻¹), indicating phonon coupling and phase coexistence. TGA/DSC demonstrates improved thermal stability, with transitions between 400 and 600 °C linked to enthalpy changes. Optical studies reveal a bandgap redshift from 1.88 eV to 1.61 eV, supported by Tauc plots and dielectric analysis. PL spectra display enhanced blue emission at ∼425 nm, associated with efficient defect-mediated recombination. Chromaticity analysis shows bluish-white emission with correlated colour temperatures (6297–6318 K) and a stable colour rendering index (∼89). The combined influence of lattice strain, phonon dynamics, and electronic transitions highlights the promise of NFO–ZrC composites for optoelectronic and photonic applications.