| abstract |
Ultraviolet (UV) radiation in the UV-C and UV-B bands, which is particularly dangerous, is absorbed and filtered by quartz and preferably between 0.065% and T.3%, glass doped with between 0.065% and 3.25%;/ by weight, of cerium metal, or cerium as such. Preferably, the cerium is added to quartz sand and/or rock crystal, in form of a fine-grained powder of up to 2 0 µm grain size, in form of cerium aluminate and preferably up to about 2%, (CeAlO3), present in up to about 5% by weight,/ and melted together in a single step. The quartz glass so obtained is particularly suitable for a metal halide discharge lamp, e.g. as an outer envelope (1), or as the discharge vessel (27) itself, or for halogen incandescent lamps, to form the quartz-glass light bulb or an envelops therefor. A small quantity of titanium oxide, up to about 0.05%, may be added as a further doping agent to the melt to further improve the UV absorption in the B and C bands. |