Compositional and structural study of B2O3–La2O3–Ta2O5–SiO2 glasses for high refractive index optical lenses

High-refractive index glasses are used to produce glass lenses by the precision optical Glass Mold Press (GMP) process and have been extensively studied because of increased demand for their application in telecommunications, optical lenses, and cameras. Borate glasses containing Ta2O5, Nb2O5, La2O3 and Gd2O3 have mainly been used as materials for GMP because of their excellent optical properties and low production cost. This study conducted a systematic investigation of the B2O3–La2O3–Ta2O5–SiO2 quaternary glass system for precision GMP applications. The glass forming range of the quaternary system was studied using (B2O3+SiO2)–La2O3–Ta2O5 and changes in physical and thermal properties such as refractive index, density and glass transition temperature of the obtained glasses were examined. Compositional dependent structural changes were also inspected by Raman spectroscopy and solid state nuclear magnetic resonance (NMR) analyses, to determine the compositions’ effect on thermal and optical properties.