Effect of Ta 2 O 5 Substituting on Thermal and Optical Properties of High Refractive Index La 2 O 3 – Nb 2 O 5 Glass System Prepared by Aerodynamic Levitation Method

High refractive index glasses with nominal composition of 0.35La 2 O 3 –(0.65− x )Nb 2 O 5 – x Ta 2 O 5 ( x ≤ 0.35) were prepared by aerodynamic levitation method. The effect of Ta 2 O 5 substituting on their thermal and optical properties was investigated. All the glasses obtained were colorless and transparent. Differential thermal analyzer results show that as the content of Ta 2 O 5 increased, the thermal stability of the glasses increased but the glass‐forming ability decreased. The transmittance spectra of all the obtained glasses exhibited a wide transmittance window ranging from 380 to 5500 nm. As the content of Ta 2 O 5 increased, the refractive index of the glasses was enhanced from 2.15 to 2.21 and the dispersion was reduced with the Abbe number increasing from 20 to 27.