Multiple layer composite electrodes for discharge lamps
AssigneePhilips Electronics North America Corporation
InventorsVivek Mehrotra, Hemant S. Betrabet, Susan McGee, Thomas F. McGee
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Abstract
Composite sintered electrodes with improved properties that make them suitable for use in a variety of lamp types, are provided which comprise a refractory metal and a substantial amount of a refractory emitter oxide, either single layer or multiple layer, the composites having been subjected to sintering at an elevated temperature effective to form a composite electrode having a density of at least 85%, preferably in the presence of a sintering activator, such as for example, Ni, or mixture thereof with a sintering aid such as, for example, Li.sub.2 O.
Claims25
An electrode comprising a composite of a refractory metal and a refractory emitter oxide selected from the group consisting of
- (a) single layer composites of a refractory metal and a substantial amount of a refractory emitter oxide containing a sintering activator or mixture thereof with a sintering aid compound;
- and
- (b) multiple layered composites comprising at least two layers of mixtures of refractory metal and refractory emitter oxide or mixtures of said oxides, at least one of said layers comprising the multiple layer composite having a different volume of emitter oxide or mixtures of emitter oxides when compared to at least one other layer comprising the multiple layer composite, at least one of the layers containing a sintering activator or mixture thereof with a sintering aid,
- said composites having been subjected to sintering at an elevated temperature effective to form a composite electrode having a density of at least about 85%, said elevated temperature being selected from the range of (i) a temperature at least above the temperature at which sintering of the refractory metal with activator is initiated and said composite density of at least about 85% is achieved and (ii) a temperature below the temperature at which (x) sintering of the refractory metal without activator is initiated and (y) the emitter oxide and/or activator undergo substantial degradation.
An electrode which comprises a multiple layer composite selected from the group consisting of:
- (1) a. Top layer:
- 75 vol. % Ba.sub.0.5 Sr.sub.0.5 ZrO.sub.3 +25 vol. % W+3 mol % Li.sub.2 O of the amount of Ba.sub.0.5 Sr.sub.0.5 ZrO.sub.3 ;
- b. Bottom layer:
- 40 vol. % Ba.sub.0.5 Sr.sub.0.5 ZrO.sub.3 +60 vol. % W+3 mol % Li.sub.2 O of the amount of the Ba.sub.0.5 Sr.sub.0.5 ZrO.sub.3 +0.2 wt. % Ni based on the amount of W;
- and
- (2) a. Top layer:
- 50 vol. % BaTiO.sub.3 +30 vol. % Ba.sub.2 TiO.sub.4 +20 vol. % W+0.2 wt. % Ni based on the amount of the W+3 mol % TiO.sub.2 based on the amount of BaTiO.sub.3
- b. Bottom layer:
- 30 vol. % BaTiO.sub.3 +10 vol. % Ba.sub.2 TiO.sub.4 +60 vol. % W+0.2 wt. % Ni based on the amount of tungsten +3 mol % TiO.sub.2 based on the amount of BaTiO.sub.3.
An electrode which comprises a multiple layer composite which comprises a layer of W+40 vol. % BaZrO.sub.3, a layer of W+75 vol. % BaZrO.sub.3, and a layer of W+40 vol. % BaZrO.sub.3,
- said composite having been subjected to sintering at an elevated temperature effective to form a composite electrode having a density of at least about 85%, said elevated temperature being selected from the range of (i) a temperature at least above the temperature at which sintering of the refractory metal with activator is initiated and said composite density of at least about 85% is achieved and (ii) a temperature below the temperature at which (x) sintering of the refractory metal without activator is initiated and (y) the emitter oxide and/or activator undergo substantial degradation.
An electrode which comprises a multiple layer composite which comprises five layers comprising a layer of W+40 vol. % BaZrO.sub.3, a layer of W+62 vol. % BaZrO.sub.3, a layer of W+75 vol. % BaZrO.sub.3, a layer of W+62 vol. % BaZrO.sub.3, and a layer of W+40 vol. % BaZrO.sub.3,
- said composite having been subjected to sintering at an elevated temperature effective to form a composite electrode having a density of at least about 85%, said elevated temperature being selected from the range of (i) a temperature at least above the temperature at which sintering of the refractory metal with activator is initiated and said composite density of at least about 85% is achieved and (ii) a temperature below the temperature at which (x) sintering of the refractory metal without activator is initiated and (y) the emitter oxide and/or activator undergo substantial degradation.
An electrode which comprises a multiple layer composite which comprises a layer of W+40 vol. % BaZrO.sub.3, a layer of W+75 vol. % BaZrO.sub.3, and a layer of W+40 vol. % BaZrO.sub.3.
An electrode which comprises a multiple layer composite which comprises five layers comprising a layer of W+40 vol. % BaZrO.sub.3, a layer of W+62 vol. % BaZrO.sub.3, a layer of W+75 vol. % BaZrO.sub.3, a layer of W+62 vol. % BaZrO.sub.3, and a layer of W+40 vol. % BaZrO.sub.3.
Dependencies are inferred from the claim text.