Modulating structural and dielectric properties of CrFeO₃ materials via Ni²⁺ substitution: Insights from rietveld refinement, elemental and spectral evaluation for high-frequency applications

Nanomaterials of CrFe_1-xNi_xO₃ (where x = 0.0, 0.1, 0.3, and 0.5) with nickel (Ni) substitution were fabricated via Auto-ignition. Sintering at 700 °C for 4 h stabilized the CrNi_xFe_1-xO₃ phase in the fabricated samples. X-ray diffraction confirmed each sample's pure rhombohedral crystal. The crystallite dimensions of the fabricated samples were within the nanometer scale (41–46 nm). The X-ray density of the material fluctuates between 4.22 and 4.86 g/cm³ due to the incorporation of Ni²⁺ ions. Rietveld refinement supported the pure-phase rhombohedral structure of the materials. Infrared spectroscopy indicated that the vibrational band ʋ₂ experienced a shift from 429 to 441 cm⁻¹ due to Ni²⁺ substitution at the octahedral sites, whereas the band ʋ₁ exhibited only minor variations. XPS elucidated all metal ions' appearance and electronic configurations within the samples. Electrical transport properties were assessed at microwave frequencies, with dielectric parameters optimized about frequency and Ni²⁺ substitution. Integrating Ni into CrNi_xFe_1-xO₃ (0.0 ≤ x ≤ 0.5) materials increases the ε′, with the maximum value attained at x = 0.3. Impedance measurements and Cole-Cole plots elucidated the contributions from grain boundaries. The materials demonstrated a minimum reflection loss of −37 dB, indicating their potential suitability for microwave absorption applications.