Coulée d'un verre tellurite
Tellurite glass casting. Research scientists place the precursors into a furnace at 850 °C to melt them. The resulting liquid is then cast in a brass mould to shape and harden it. Glass has the advantage that it is easily moulded, unlike ceramic, which often requires milling in order to shape it. In the furnace, the glass first crystallises before restructuring, thereby becoming a ceramic. Here, research scientists are trying to retain the same composition as the glass for the ceramic. The precursors used (oxide powders) must be very pure. The process is used for tellurite, niobium and bismuth glasses. These small glass parts will chiefly be used for optical fibres.