High Refractive Index of 0.30La 2 O 3 –0.70Nb 2 O 5 Glass Prepared by Containerless Processing

A high-refractive-index glass with the composition of 0.30La 2 O 3 –0.70Nb 2 O 5 was prepared in bulk form by containerless processing without using network former oxides. The glass transition temperature was 725 °C and the first crystallization peak temperature was 805 °C. The glass was colorless and transparent from 345 nm to 7.3 µm. The refractive index was higher than 2.3 in the visible range, and the Abbe number estimated from the Drude–Voigt relationship was 20.4. These results indicate that the niobate glass system would be useful for optical applications in the visible to infrared region.