Impact of SnO2 doping on spectroscopic characteristics of the SnO2-Na2O-CoO-B2O3 borate glass matrix

Abstract

The role of tin oxide (SnO₂) on the structure-optical features of borate glasses containing low cobalt oxide impurities was studied. The study was carried out on a glass system [x ${\text{SnO}}_2$ – (80-x) $B_2{O}_3$ – 19.5 ${\text{Na}}_{2}O$ – 0.5 CoO]; x = 0.0, 0.5, 1.0, 2.0 and 3.0 mol%. Glass synthesis was carried out by the melt-quench technique. Structure and optical absorption spectroscopy were carried out to explore the optical transitions of Co cations inside the present glass matrix. The obtained results indicate that, with the further addition of ${\text{SnO}}_2$ content, the molar volume decreased from 31.675 ${\text{cm}}^3/\text{mol}$ to 29.147 ${\text{cm}}^3/\text{mol.}$ FTIR studies indicated the basic structural units of trigonal BO₃ units and BO₄ tetrahedra. Herein also, additional contents of tin oxide increased the nonbridging oxygen contents. The reason behind such increment is attributed to the existence of ${\text{Sn}}^{4+}$ ions in octahedral coordination acting as network modifiers. Optical absorption spectra indicated the existence of Co ions in both Co²⁺ and Co³⁺ oxidation states. Moreover, the existence of significant SnO₂ concurred with the significant blue shift in the visible absorption bands and red shift in near infrared absorption bands. The positions absorption bands of Co ions were analyzed in the context of ligand field parameters determinations. The obtained data of the crystal field splitting parameter (10Dq_t) showed decreased values from 3451 cm⁻¹ to 3364 cm⁻¹ with more SnO₂ addition. While Racah parameter B values were also, attained showing increased values from 967 cm⁻¹ to 985 cm⁻¹ when additional SnO₂ is added. Further, the impacted role of SnO₂ addition on the structural and optical properties of the present glasses was finally estimated.