Structural, physical, and elastic properties of α-Fe2O3 nanoparticles doped on borate glasses

This study investigates the influence of α-Fe2O3 nanoparticles (NPs) on the optical, elastic, structural, and physical properties of borate glasses synthesized via the melt-quenching technique. The glass system investigated has the molar composition (68-x) B2O3-20CaO-2P2O5-10Na2O-xα-Fe2O3 (x = 0, 0.5, 1, and 2 mol%). Structural analysis using X-ray Diffraction (XRD) confirmed the amorphous nature of all glass sample’s. Fourier-Transform Infrared (FTIR) spectroscopy revealed the presence of structural units containing both three-coordinate (BO3) and four-coordinate (BO4) boron atoms within the glass network. A clear structural compaction was evidenced by the simultaneous increase in density and decrease in molar volume as the Fe2O3 content increased. Optically, the indirect optical band gap (Eg) significantly decreased from 3.138 eV to 2.36 eV, concurrently with an increase in the refractive index. This suggests an increase in non-bridging oxygen concentration and enhanced polarizability. Concurrently, elastic measurements revealed a decrease in the elastic moduli with increasing Fe2O3 concentration, consistent with a weakening or structural rearrangement of the network. Furthermore, several other physical parameters, including packing density, glass dissociation energy per unit volume, optical basicity, polarizability, and average electronegativity, were calculated and discussed as a function of Fe2O3 concentration, providing comprehensive insight into the structural role of the nanoparticles.