Corrosion resistance of a ceramic refractories and platinum to lead-phosphate glasses

High quality optical glass parts can only be successfully made in a Pt crucible. However, the UV transmission of the glass is, at the same time, significantly reduced. Glass fragments are often cured in a ceramic vessel and then overcured in a Pt crucible; the most reactive stage of the heating is the first stage and, on overcuring, high uniformity with low Pt corrosion is ensured. The interaction of specially developed phosphate flint glass, which is transparent in the near-UV, with ceramic materials used in glassmaking vessels and also with platinum was studied. The glass is based on Ba(PO3)2-Pb(PO3)2. Pure quartz containing only 0.01% colorant, synthetic aluminosilicate containing only 0.05% colorant, and zircon containing 0.1% colorant (but with high corrosion resistance) were used as refractory vessels. Corrosion tests on these vessels using the molten glass showed that the zircon was least corroded and the aluminosilicate most corroded. Interaction between the glass melt and platinum was also studied; for some lead phosphate glasses, Pt vessels can be used. The ceramic materials examined are very pure and corrosion resistant, and can be used in vessels for making near-UV transparent lead phosphate flint glass. However, to assess the feasibility of using Pt crucibles for overcuring, it is necessary to develop glasses of special composition and carry out preliminary studies on them to establish the optimal time and temperature curing schedule.