[formula omitted] Mössbauer, optical and structural properties with ligand field effects of borosilicate glass doped with iron oxide

Abstract

Here, an investigation of borosilicate glass doped with iron oxide and prepared by classical melt-quenching method. The internal macrostructure, optical absorbance, ligand field parameters, and Mössbauer spectra were studied. The density increased with increasing SiO2 content, while Fourier-transform infrared (FTIR) analysis reported that BO4 and SiO4 content increase with a decrease in NBO content. Optical electronic transitions through wavelength (402–948 nm) confirmed the existence of Fe3+ state, while the Fe2+ is not observed in optical absorbance because of its inane electronic transition at 2222 nm. The electronic transitions at (402, 452, 513, 602, and 701 nm) are assigned to Fe3+ in tetrahedral coordination (FeO4), while the electronic transitions at (795 and 948 nm) are related to Fe3+ in octahedral coordination (FeO6). Astonishingly, the ligand field parameters of Fe ions were studied. The crystal field splitting exhibits increasing values, while Racah parameters exhibit decreasing values. Moreover, nephelauxetic parameters reflect the propensity of the bonding nature between the Fe cations and their ligands towards a higher covalent nature with SiO2 additives. Further, a scant decrease in the optical band gap was explained based on the mixed former effect. Moreover, non-linear refractive indices augment with SiO2 addition. The decrease in the optical gap energy justified such a trend. Bewitchingly, Mössbauer spectra reported the existence ofFe3+ ions with isomer shift (0.285–0.314) mm s−1 in tetrahedral sites, while Fe3+ ions with isomer shift (0.339–0.425) mm s−1 in octahedral sites, agreeing with optical data. Surprisingly, Fe2+ ions with isomer shift at about 0.905 mm s−1 in tetrahedral sites was observed. The observed decrease in isomer shift of all phases is due to the decrease in electronegativity of formers. Furthermore, the decrease in quadrable splitting is attributed to the decline in the polarization power of the glass former cations with SiO2 addition.