Ligand field parameters, optical, thermal, magnetic, and structural features of ZnO containing cobalt-borate glasses

Abstract

This article presents a study of cobalt speciation in borate glass samples, with up to 20 mol. % of zinc oxide. The samples were prepared by the melt-quenching method. The glass properties were presented utilizing a set of complementary investigations of all samples to evaluate structural, optical, thermal, and magnetic properties. XRD technique was exploited to scrutinize the structural nature of samples. Macrostructural modifications were demonstrated using Archimedes’ principle. FT-IR was utilized to probe the internal components of the glass network. Thermograms analysis was used to determine the thermal stability of the samples, which is required for applications. Optical band gap energy was decreased while the Urbach energy was enhanced. Using ligand field theory of cobalt ions, the optical absorption transitions were studied of Co2+ ions. Astonishingly, the usability of ligand field theory to evaluate the optical parameters was presented, in addition to their relation to the structural changes was demonstrated. Non-linearity aspects were enhanced with ZnO addition. Finally, ESR signals confirmed the existence of Co2+ ions in octahedral and tetrahedral symmetry, with a possibility of tetrahedral ions converting to octahedral symmetry. Based on the evaluation of ligand field parameters, besides the structural, optical, thermal, and magnetic features due to ZnO addition, our study reveals a significant potential for utilizing Zn-BNC glass for different optoelectronic purposes.