New lead-free optical heavy crown or double-heavy crown glass

摘要

A novel lead-free optical heavy crown or double-heavy crown glass, with a refractive index (nd) of 1.60-1.65 and an Abbe index (vd) of 50-60, has the composition (by wt., on oxide basis) 20-37% SiO2, 8-20% B2O3, 43-55% BaO, 0.01-10% ZnO, 0-7% CaO, 0-7% MgO, 0.01-5% TiO2, 0.01-7% ZrO2, 0.1-10% Al2O3, 0-8% Na2O, 0-8% K2O, less than 3% La2O3, 0-1% F-, 0-3% P2O5 and optionally usual amounts of refiners, the sum of CaO + MgO being 0-7%, the sum of BaO + ZnO + CaO + MgO being less than 60% and the sum of Na2O + K2O being 0-8%.