Optical Borate Glasses Of High Refractive Index And Low Dispersion Practically Free From Toxic And Radioactive Crude Materials

Optical glasses with RI above 1.7 and Abbe values above 47 consisted essentially of: at least 80 (wt%) of a mixture of boric oxide, lanthanum oxide, and at least 1 of the oxides of Mg, Ca, Si, and Ba, in which the molecular ratio of the latter oxide to B2O3 is 0.148-0.5; 0-20% of at least one of the oxides of Ge, Sn, Zr, and Ta; 0-5% of (SiO2 + Al203). La203 could be at least partly replaced by Y203 or M203. Other claims covered: GeO2 content (wt%) 0-10, Zr02 0-20, SnO 0-5, Ta205 0-25. 8 glass compositions are given.