Patent ID: 6046544
Filing Date: 2000-04-04
Classification: H01J

Abstract:
A high-pressure metal halide discharge lamp comprising a light-transmitting lamp vessel which is sealed in a vacuumtight manner and contains an ionizable filling including an inert gas and a metal halide, and in which tungsten electrodes are arranged, which are connected to current conductors which issue to the exterior through the lamp vessel, which electrodes are provided with an emitter comprising tungsten and a first oxide selected from hafnium oxide and zirconium oxide, a second oxide consisting of lanthanum oxide, and a third oxide consisting of at least one oxide selected from the group of oxides of the elements yttrium and the lanthanides, said electrodes and emitter being substantially free of thorium oxide, the second oxide accounting for M mol % of the sum of the second oxide and the first oxide, the third oxide having a weight percentage M3 in the emitter, and M and M3 having the values listed in Table 1TABLE1  M3 third oxide (absolute wt.% first oxide second oxide M (III) III in the (I) (II) (mol % II) atomic no. emitter)  ZrO.sub.2 La.sub.2 O.sub.3 48-98 39 0.05-10 HfO.sub.2 La.sub.2 O.sub.3 48-98 39 0.05-10 ZrO.sub.2 La.sub.2 O.sub.3 48-98 58 through 71 0.05-15 HfO.sub.2 La.sub.2 O.sub.3 48-98 58 through 71 0.05-15.