Fabrication of Lead-Free High Refractive Index Glass Using Local Raw Materials

High refractive index glass can be made by adding a heavy metal ion such as lead into glass. Lead contained glass can be melt at low temperature. Due to the harmful effects of lead, there are several attempts on using other materials to replace lead as much as possible. In this study, the lead-free high refractive index glasses were made by using local raw materials and by adding barium carbonate to replace lead in a mixture with various contents. The main composition of the mixture consisting of glass sand, dolomite, feldspar, limestone, sodium carbonate and boron oxide was poured into the crucible and melted in an electric furnace, in the normal atmosphere at a temperature of 1250°C for 6 hours. The refractive indices of glass specimens were found to increase from 1.5602 to 1.6784 as the increase of the additional amount of barium carbonate from 24% to 40%. Results from a comparison study in the 32% barium or lead contained glasses prepared from various places local sand was found that the average refractive index of the barium glass and lead glass were 1.63 and 1.67 respectively. The dwell time of the barium glass was found longer than that of the lead glass.

Keywords: lead free, high refractive index, local raw materials, glass

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