Multiple layer composite electrodes for discharge lamps and low temperature co-sintering method for producing the same
AssigneePhilips Electronics North America Corporation
InventorsVivek Mehrotra, Hemant S. Betrabet, Susan McGee, Thomas F. McGee
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Abstract
Lamps that include composite sintered electrodes with improved properties that make them suitable for use in a variety of lamp types, are provided by a method for producing electrodes which comprise a refractory metal and 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.
Claims37
A method for producing a multiple layered composite electrode which comprises the steps of:
- (a) mixing a refractory metal powder with different volumes of an oxide emitter powder selected from the group consisting of (a) single layer composites of a refractory metal and a refractory emitter oxide containing an effective amount of a sintering activator or mixture thereof with a sintering aid compound;
- and (b) multiple layered composites comprising at least two layers of of mixtures of refractory metal and refractory emitter oxide or mixtures of said oxides, said layers having different volume fractions of emitter oxide or mixtures of emitter oxides, at least one of the layers containing an effective amount of a sintering activator or mixture thereof with a sintering aid compound,
- (b) depositing a first refractory metal powder/oxide emitter powder mixture to form a base layer;
- (c) depositing at least a second refractory metal/oxide emitter powder mixture to form a top layer adjacent to the base layer;
- (d) pressing the deposited layers to form a multilayered body;
- and
- (f) sintering said multilayered body 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 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.
A method as claimed in claim 9, wherein said emitter oxide is barium strontium zirconate.
A method for producing a multiple layered composite electrode which comprises the steps of:
- (a) mixing a refractory metal powder with different volumes of an oxide emitter powder;
- (b) depositing a first refractory metal powder/oxide emitter powder mixture to form a base layer;
- (c) depositing at least a second refractory metal/oxide emitter powder mixture to form a top layer adjacent to the base layer;
- (d) pressing the deposited layers to form a multilayered body;
- and
- (f) sintering said multilayered body 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 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.
A method for producing a multiple layered composite electrode which comprises the steps of:
- (a) mixing a refractory metal powder with different volumes of an oxide emitter powder;
- (b) depositing a first refractory metal powder/oxide emitter powder mixture to form a base layer;
- (c) depositing at least a second refractory metal/oxide emitter powder mixture to form a top layer adjacent to the base layer;
- (d) pressing the deposited layers to form a multilayered body;
- (f) sintering said multilayered body 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 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;
- and
- (g) removing refractory metal from the top layer of the electrode to a depth of about 10-50 .mu.m by dipping the electrodes in a solution of hydrogen peroxide at a temperature of about 50.degree. to about 80.degree. C.
A method of forming a composite electrode which comprises the steps of:
- (a) mixing a refractory metal powder with an oxide emitter powder and an effective amount of at least one sintering activator;
- (b) pressing the mixture to form a composite body;
- and
- (f) sintering said composite body at a temperature within the range of about 1100.degree. C. to about 1400.degree. C.
A method of forming a composite electrode which comprises the steps of:
- (a) mixing a refractory metal powder with an oxide emitter powder and an effective amount of at least one sintering activator;
- (b) pressing the mixture to form a composite body;
- (f) sintering said composite body at a temperature within the range of about 1100.degree. C. to about 1400.degree. C. and
- (g) removing refractory metal from the top layer of the electrode to a depth of about 10-50 .mu.m by dipping the electrode in a solution of hydrogen peroxide at a temperature of about 50.degree. to about 80.degree. C.
A fluorescent lamp which includes an electrode which comprises 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 refractory emitter oxide containing an effective amount of a sintering activator or mixture thereof with a sintering aid;
- and (b) multiple layered composites comprising at least two layers of mixtures of refractory metal and refractory emitter oxide or mixtures of said oxides, said layers having different volume fractions of emitter oxide or mixtures of emitter oxides, at least one of the layers containing an effective amount of 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 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.
A fluorescent lamp which includes a multiple layer composite electrode selected from the group 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.
Dependencies are inferred from the claim text.