TUNGSTEN-FLUORINE LAMPS WITH A PASSIVATION LAYER OF ALUMINUM FLUORIDE TO PROTECT FUSED QUARTZ ENVELOPES FROM ATTACK BY FLUORINE

Solid dosed tungsten-fluorine lamps have improved life compared to bromine lamps. Lamps remain clean through life. Protection of the lamp envelope from attack by fluorine is due to a passivation layer of aluminum fluoride formed by reaction of an internal Al2O3—TiO2—P2O5 glass coating with fluorine in the lamp atmosphere.