Glass-forming ability of high refractive index amorphous materials prepared by TiO2 and Nb2O5

Abstract By using a laser pneumatic suspension furnace, a series of transparent 0.3LaGaO3-(0.7 − x)TiO2-xNb2O5 amorphous spheres with diameters of approximately 2–4 mm can be obtained with an x-value between 0 and 0.65. An approximate value for the critical cooling rate was obtained using CCT diagrams. The four criterions of GFA (glass forming ability) were discussed in terms of the R2 value; the higher the R2 value, the better the linear relationship between GFA and the critical cooling rate. The maximum value of R2 was obtained for the Rc-ΔT (Rc is defined as the critical cooling rate) plot. The ΔT was chosen as a GFA criterion to evaluate the GFA of LaGaO3-TiO2, LaGaO3 Nb2O5 and LaAlO3 Nb2O5 amorphous spheres. The GFA of four series of highly-refractive amorphous spheres prepared by TiO2 and Nb2O5 are also discussed. The maximum transmittances of 0.3LaGaO3-(0.7 − x)TiO2-xNb2O5 amorphous samples, where x = 0.1, 0.2 and 0.3, were approximately 78%, 76% and 75% respectively. The refractive index nd of the amorphous samples were all higher than 2.2.