MODIFICATION OF ZNMN₂O₄ WITH LA IONS: STRUCTURAL STABILITY AND PROPERTIES

Abstract

The article presents the synthesis and comprehensive study of the physicochemical properties of lanthanum-substituted spinels with the composition Zn(1-x)LaxMn2O4 (x = 0.05, 0.10, 0.15, 0.20), obtained via the sol-gel method. The primary focus is on the effect of substituting zinc ions with lanthanum on the crystalline structure, phase composition, and physical properties of the materials. A multi-method approach was applied, including Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. It was found that all samples are single-phase, regardless of lanthanum content, indicating the stability of the spinel structure even at the highest lanthanum concentration. The crystallite sizes were estimated using the Scherrer equation. The Rietveld refinement method allowed for a detailed analysis of the crystal structure, including the determination of key unit cell parameters and X-ray density. FTIR data indicate the presence of three characteristic absorption bands in the 1000–400cm⁻¹ range across all samples, with a gradual shift of one absorption band towards the longer wavelength region as substitution increases. The bandgap, calculated using the Tauc graphical method, ranges from 2.11eV to 2.8 eV at different levels of zinc substitution. SEM analysis revealed a large effective surface area and high porosity of the synthesized samples, highlighting their potential for applications in fields such as catalysis, sensing, and energy. The results demonstrate that the gradual substitution of zinc with lanthanum enables control over material properties, specifically the bandgap and porosity, making these materials promising for high-tech applications.