An investigation into the morphology and crystallization process of lithium borate glass containing vanadium oxide

Abstract

A series of lithium borate glasses with V2O5 were successfully prepared by melt annealing. The glass-ceramics were made by heating the glass to the glass transition temperature (Tg), then heating it to the crystallization temperature (Tc), converting it from a vitreous state to a crystalline state. This study found a link between the glass transition (Tg) and V2O5 ratio in the host glass, with Tg rising from 345 °C for base glass to 419 °C for glass containing 2% V2O5. The glass stability of the base sample was higher than that of the V2O5 samples. XRD analysis revealed the main crystalline phase in the derived glass-ceramics to be Li2B4O7 tetragonal, with crystalline traces of Li2B2O4.16H2O phase. Similarly, crystallite growth on plane (112) decreased from 253 Å (the base) to 239 Å (2% V2O5). Vitreous structure was existed in the glass samples, while spherical particles were found in the derived glass-ceramic materials. The spherical particles began to take on large geometric shapes as the V2O5 content increased from 1% to 2%. All glass-ceramic samples have traces of vitreous material. Glass and glass-ceramics with structural units of BO3, BO4, boroxol rings, and B–O–B linkages were also presented. The phonon-energy (Eph) and optical transition (Eg) showed a strong correlation with V2O5 content. As V2O5 increased between the conduction and valence bands, Eph increased from 99 to 232 meV and Eg decreased from 3.164 to 2.250 eV.