ABSTRACT Colorless and transparent La 2 O 3 –Nb 2 O 5 –WO 3 (LNW) glasses were successfully synthesized using a levitation technique in a wide glass‐forming region. These glasses exhibited excellent optical properties, including a high refractive index (>2.1) with low wavelength dispersion, and high transmittance (70%‒75% at a thickness of ∼800 µm) in the ultraviolet–visible region. The glass transition temperature decreased with increasing WO 3 content, reaching as low as 550°C, which enables easier pressing and molding compared to other levitation‐synthesized high‐refractive‐index glasses, such as Nb 2 O 5 ‐based and TiO 2 ‐based glasses. The dependence of the packing density and the electronic polarizability of the oxide ion on the Nb 2 O 5 content suggested that the effect of substituting Nb 2 O 5 with WO 3 substantially differs between La 2 O 3 ‐rich and Nb 2 O 5 ‐rich La 2 O 3 –Nb 2 O 5 binary glasses. The inherent absorption wavelength decreased with increasing WO 3 content, resulting in a lower wavelength dispersion of the refractive index. These findings indicate that LNW glasses are promising optical materials for advanced applications requiring high refractive index and low processing temperature.
Chengzhong et al. (Sun,) studied this question.