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

Abstract

Owing to the ultrahigh refractive index, La 2 O 3 -TiO 2 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, La 2 O 3 -TiO 2 glasses were successfully prepared by hot-press sintering within the glass kinetic window. A small amount addition of SiO 2 was found to effectively increase the glass-forming ability while keeping high refractive index. When the content of SiO 2 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. K E Y W O R D Scontainerless solidification, glass, high refractive index, hot-pressed sintering, La 2 O 3 -TiO 2 ORCID Jianjun Hanhttps://orcid.org/0000-0003-3266-4971Jianqiang Li https://orcid.org/0000-0002-9591-458XGang He https://orcid.org/0000-0002-9691-0679

Crystallization of glass materials into transparent optical ceramics

“…Additionally, the same group also demonstrated how the limits in the size of the samples prepared via the ADL method could be overcome by sintering the powder of the crushed ADL-prepared glass beads in a hot-press sintering furnace to obtain larger sized (∼10 mm in diameter) glass samples at relatively low temperature and low pressure. Although not fully crystallized, the authors obtained highly transparent bulk La 2 O 3 -TiO 2 glass samples with the addition of a very small amount of SiO 2 as an additive that simultaneously suppressed the crystallization and aided the glass-forming ability [139]. Similar results were also observed in two other systems, La 2 O 3 -Nb 2 O 5 [140] and La 2 O 3 -TiO 2 -ZrO 2 [141], where the transparent glass samples of larger size and high density were obtained as a result of the plastic flow mechanism during the hot-press sintering.…”

Structural, Thermal, and Optical Properties of GeO2-La2O3-TiO2 Glasses

“…However, the glasses prepared by such methods are too small to be applied. Generally, the diameter of glass spheres prepared by containerless methods does not exceed 10 mm [14] , which limits the applications in large-size optical lenses, tank perimetry, infrared windows, etc. By hot-pressed sintering, largesize lanthanum titanium glass can be prepared.…”

“…By hot-pressed sintering, largesize lanthanum titanium glass can be prepared. However, because the glass prepared by this method is too colored and has a maximum transmittance of 54% in the visible light region [14] , it cannot be used as a material for the preparation of optical lenses and windows. Therefore, in order to obtain large-size highrefractive index lanthanum titanium optical glass, it is meaningful to find a suitable network former and find a balance point between size and high refractive index, and prepare large-size high-refractive index lanthanum titanium optical glass by high-temperature melting method.…”