Large-sized La2O3-TiO2 high refractive glasses with low SiO2 fraction by hot-press sintering

Owing to the ultrahigh refractive index, La2O3-TiO2 glass is regarded as a promising candidate material in the field of lens, gemstones, and many other optics. However, due to its extremely low glass-forming ability, it can only be obtained by rapid solidification processes such as melt quench or containerless solidification methods, leading to the limited size of as-solidified products (for example, 1-10 mm for containerless solidified sample), that are severely deferring the application of this novel high refractive glass. In this work, we aimed at preparing the larger sized bulk glasses over 10 mm, La2O3-TiO2 glasses were successfully prepared by hot-press sintering within the glass kinetic window. A small amount addition of SiO2 was found to effectively increase the glass-forming ability while keeping high refractive index. When the content of SiO2 was 15 mol%, its transmittance could reach 54% at 800 nm and 72% in the infrared region (1 mm thick). Meanwhile, its refractive index could keep ultrahigh value above 2.14. And the sintering mechanism was studied according to the sintering shrinkage curve. It indicates that the plastic flow was the main mass transfer way in the densification process.