New lead-free barium flint glass

摘要

The lead-free barium flint glass, having a refractive index (nd) of 1.55-1.66 and an Abbe value (vd) of 39-52), has the composition (by wt., on oxide basis) 40-60% SiO2, 6.5-12% B2O3, 10-35% BaO, 0-1% CaO, 0-2% ZnO, 5-12% TiO2, 0.5-3.5% Al2O3, 3-7.5% Na2O, 3-8% K2O and optionally usual amounts of refiners, the sum of Na2O + K2O being <= 15%. Preferred glass compositions are (i) 41-48% SiO2, 6.5-8% B2O3, 28-35% BaO, 0.5-1% CaO, 1-2% ZnO, 5-12% TiO2, 0.5-1.5% Al2O3, 3-5% Na2O, 3-5% K2O and optionally usual amounts of refiners, the sum of Na2O + K2O being 6.5-8% and the refractive index (nd) being 1.60-1.66; (ii) 46-59% SiO2, 6.5-8.5% B2O3, 10-28% BaO, 0.1-1% CaO, 0-2% ZnO, 6.5-12% TiO2, 0.5-2% Al2O3, 3-7.5% Na2O, 3-7.5% K2O and optionally usual amounts of refiners, the sum of Na2O + K2O being /-6.5% and the refractive index (nd) being 1.56-1.61; and especially (iii) 43-57% SiO2, 7-11% B2O3, 11-26% BaO, 0.1-0.5% CaO, 0-1.5% ZnO, 7.5-11% TiO2 , 0.8-3% Al2O3, 3.5-7% Na2O, 3.5-7.5% K2O and optionally usual amounts of refiners, the sum of Na2O + K2O being <= 14% and the refractive index (nd) being 1.57-1.61.