JPS6035422B2 - Conductive cermet and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to conductive cermets, their manufacture and their use in the manufacture of arc tubes and other electric lamps.

The present invention also relates to a method of sealing the end of a light bulb and discharge device, and parts therefor. Lack of ductility is one of the major material limitations of ceramic refractory oxides, and this imposes severe limitations on the design of ceramic structural components.

Even at temperatures above mid-melting point, the number of independent effective slip deformation systems is insufficient to even meet the minimum of five effective slip deformation systems for ductility. Although the strength of ceramic materials can be significantly improved by reducing the size of the oxide particles and by reducing the porosity by adding appropriate additives, the destructive stress increases. and cause severe damage. One way to improve the resistance to crack initiation and propagation is to increase the magnitude of the fracture surface energy by at least an order of magnitude. This durability enhancement can be achieved by incorporating one or more ductile layers within the ceramic lattice, where the amount and geometry of the second layer incorporated may vary. It has a great effect on strengthening the fragile matrix and increasing its durability. A cermet is defined as a ceramic material containing a proportion of metal as a separating layer.

An example of a cermet is an alumina ceramic containing Mo, W, and Fe. Such cermet materials are either electrically insulators or conductors, depending on the relative proportions of oxide and metal, and the size and distribution of metal particles in the bonding material. The incorporation of ductile metal layers provides conventional ceramic materials with increased mechanical strength and durability as well as resistance to thermal shock. Recently, in British Patent No. 1,382,934, a volume fraction of 0
．． Alumina/molybdenum containing 34 molybdenum
The use of cermets for sealing the ends of alumina ceramic arc tubes in high-pressure sodium lamps is disclosed, and another British Patent No. 1,361,773 describes the use of cermets for the same purpose, with The use of aluminanomolybdenum cermets containing molybdenum is disclosed.

The main advantage of this method is that other end seals
Unlike case al), the electrode does not penetrate the cermet cap, thereby avoiding a difficult weld seal between the electrode and the cap. Also, a drawback of this method is that the cermet and alumina arc tube expansions do not match over the temperature range in which it operates (typically ambient to 900° C.), causing distortion in the seal. This distortion can cause cracks and leaks in the cap or tube. Until very recently, most conductive cermets had to contain a relatively large amount of metal (usually at least 0.2 by volume) in order to conduct electricity (hereinafter referred to as " volume ratio
The term ``ction'' refers to the ratio of the volume of the entrained metal to the volume of the ceramic, both calculated in terms of completely theoretical densities in separate and independent states. The amount will significantly affect its thermal expansion properties and will correspondingly increase its thermal expansion incompatibilities.
Sealing using Ceramic Caps (Corning, Inc.) has to date exposed various technical problems.

For example, it has been found that as the diameter of "coaster" tubes increases, the tendency for ends to crack during sealing operations also increases. This is partly due to the mismatch between the coefficients of thermal expansion along the a- and c-axes of the "coaster" and that of polycrystalline alumina; This is due to the fact that they are more likely to cause fatal damage. The tendency of "coasters" to crack is generally due to the fact that the material is not a true single crystal but has some grain boundaries.
This results in making the material brittle. The present invention has found a way to overcome these difficult problems by using superior cermet materials and superior methods of sealing ceramic envelopes or manufacturing lamps and caps. These discoveries are “coasters”
The same applies to ceramic arc tubes. According to a first aspect of the invention, refractory oxide particles, for example alumina, surrounded by a thin layer of at least one metal selected from the group consisting of W, Mo, Cr, Fe, Ni A conductive cermet is obtained.

The thin layer of metal in the cermet constitutes an electrically conductive network that extends throughout the cermet. This allows conductive cermets with a low volumetric proportion of the metals contained and thus with a coefficient of thermal expansion approximately equal to that of refractory oxide ceramics, such as polycrystalline alumina. This novel cermet is produced by rolling together fine metal powder and coarse jaw grains or bulk oxides until the latter are uniformly coated with metal powder, then compressing the metal powder-coated oxide grains. It can be produced by hardening and subsequent freezing in a furnace.

The actual size of the particles does not need to be very precise except when manufacturing special cermets as described below.

However, in order for the oxide jaws to become coated with metal powder during the rolling operation, the particles of metal powder must be sufficiently finer than the oxide jaws. The metals used in the production of very low metal content oxide/metal conductive cermets are not limited to tungsten or molybdenum as described above.

In addition, chromium, iron, nickel, etc. can be easily mixed into cermet. These can be mixed as a substitute for tungsten or molybdenum, or in addition to them. Cermets are sintered or hot pressed under vacuum or gas conditions such as argon or hydrogen. Refractory oxides in cermets include, for example, AI, Mg, Be, Y, Hf, Zr, T
As with the oxides of h, there can be a wide diversity in its chemical composition. This may be a mixture of oxides, such as spinel, or impurities, such as Mg, Y, or insulators contained in AI203, or e.g. Mg0, Y203, YQ03. It is sometimes used as an additive to aid in dawning. The techniques provided by the present invention for sealing "coaster" and polycrystalline alumina arc tubes can also be applied to sealing other ceramic tubes.

Further, according to this aspect of the invention, the particles have an average diameter of 4
By using refractory oxide grains of 00 to 800 microns and metal powder with an average particle diameter of less than a micron, insulation or conductivity can be achieved by selecting the volume ratio of the metal and/or the size of the oxide grains. It is possible to manufacture any desired type of cermet.

In particular, when using tungsten with a volume ratio in the range of 0.045 to 0.067, conductive cermets can be made using oxide grains in the range of 400 to 800 microns, and smaller oxide grains can be used. Insulating cermet can be made using the grains. Both of these cermets have the same metal volume ratio and therefore the same coefficient of thermal expansion. This coefficient of thermal expansion is very close to that of pure oxide ceramics. In understanding the description of the average particle size of the oxide particles and metal powder used in producing the cermet according to the present invention, the following should be noted.

That is, it is difficult to determine the particle size in the region covered by the present invention with complete precision, and the limit value or desired value should be interpreted and applied as appropriate depending on each individual case. That's what it means. A second aspect of the invention provides that a light bulb, a discharge tube or a component thereof is combined with a cermet part (e.g. an alumina/tungsten conductive cermet). A composite structure consisting of a ceramic part (sintered alumina ceramic)
structure).

The tubes or parts of these hybrid structures can be manufactured as monolithic or unitary structures by pressing layers of component materials together in different proportions and further scaling the resulting loose agglomerate mixture. can. Further, in accordance with this aspect of the invention, an annular shape for sealing the end of a ceramic arc tube or incandescent lamp envelope is constructed at least in part of a conductive cermet and conforms to the end wall of said tube or envelope. An end cap with a groove is formed.

The cap is placed over the end wall of the tube and sealed with a glass frit (eg, a conventional magnesium aluminate frit). This method of sealing an alumina arc tube is particularly suitable for the construction of high pressure sodium lamps or metal halide lamps. The present invention also provides a method of making and a method of using a hybrid cap consisting of insulating and conductive cermets having the same metal volume ratio and having virtually no difference in coefficient of thermal expansion. Caps of such hybrid structures are formed of two or more regions of conductive cermet separated by regions of insulating cermet and can be used to seal tubes or bulbs with one open end. .
They are also preferably formed with an annular groove that fits into the tube wall. {11 Regarding conductive cermets, generally speaking, the cermets of the present invention are selected from the group consisting of refractory oxide grains with an average diameter of 50 to 800 microns and W, Mo, Cr, Fe, and Ni with an average diameter of 12 microns or less. and at least one kind of metal powder.

In general, the finer the metal powder, the better, preferably with an average diameter of 1 micron or less.

Metal powders up to 12 microns are suitable for the coarsest class of oxide grains.

The metal volume ratio is 0.067 or more (more specifically 0.0
67 to 0.2), the average diameter of the particles is 5 to 8
Conductive cermets can be produced using 0.00 micron (more specifically 50 to 200 micron) oxide grains.

A cermet manufactured from oxide grains in this range becomes a conductive cermet if the volume ratio of the metal is 0.067 or more, and cannot be electrically conductive if the volume ratio of the metal is less than 0.067. However, if the oxide particles have a large average diameter of 400 to 800 microns, it is possible to obtain a conductive cermet even if the metal volume ratio is as low as 0.045.

However, when using small oxide grains (preferably less than 100 microns, especially less than 50 microns), simply select the size of the oxide grains, since at such low metal volume ratios an insulating cermet is obtained. By doing so, it is possible to produce electrically conductive and insulating cermets in which the volume ratio of the metals is the same and therefore the properties such as thermal conductivity are the same.

When manufacturing cermets of the latter type, the size distribution of the oxide grains is in a relatively narrow range (e.g. 400-800
In the case of 00 microns, it is desirable to limit the average value to within ±50 microns). On the other hand, in the former type, especially when producing conductive cermet with a metal volume ratio of 0.067 or more from oxide grains in the range of 5 to 200 microns, the narrow distribution of particle sizes is not so strong. not important. The free-flowing alumina granules passed through the metal deposition described herein have an average particle diameter of 0.3 French m, a surface area of 30/g and a purity of 99.98% Q or Y alumina powder LK9 in deionized water. for 6 hours with 0.05% by weight of magnesium oxide (to increase density and promote uniform particle growth).

The resulting slurry is subsequently dried, sieved through a 710 micron mesh, and rolled freely to clump most of the particles less than 50 microns in diameter. The granulated material is then sieved through meshes of various sizes to achieve a final size within a specific diameter range. In addition to magnesium oxide, a rare earth oxide such as yttrium oxide or ytterbium oxide may be added in an amount of about 0.1% by weight in order to lower the sintering temperature. The size of the grains can be controlled by the rolling time, and increases as the rolling time increases.
For example, grains with a size of 200 Buddhas can be produced by rolling for 20 minutes, but if necessary, rolling may be extended to, for example, one hour or more. It has been found that it is desirable to add magnesium oxide during processing of the alumina powder in order to uniformly redistribute the strain within the alumina grains. As for the addition of magnesium oxide, it is preferable to add 0.05% by weight of free magnesium oxide in the examples described above.

Addition of large amounts of magnesium oxide, up to 0.25% by weight, further reduces the size of the sintered alumina particles and thus increases the strength of the cermet.

A preferred effective amount of magnesium oxide added is 0.01 to 0.25% by weight. An example of a material suitable for sealing an alumina arc tube is a cermet made of AI203 and W (volume ratio of W is 0.072). The electrical resistance value of this material is approximately 5×10-3 ohm. cm. And loo. The coefficient of thermal expansion from 0 to 900 oo is only 5 x 10-7/°C (which is less than that of polycrystalline alumina).

This kind of conductive cermet of alumina/tungsten consists of 28.5% by weight of tungsten powder, preferably of near-spherical shape (99.95% purity, average diameter 1 French meter) and alumina powder with an average diameter of about 200 French meters. It can be manufactured by mixing with grains.

The mixture is then rolled between two vessels to deposit a uniform coating of tungsten powder on the alumina grains. 0.
Materials of this type have been produced with various metal volume ratios from 0.067 to 0.2 and have shown satisfactory electrical conductivity in the fired state.

A conductive cermet with a small metal volume ratio (0.045) was obtained using relatively large oxide grains with a diameter of 400 to 800 microns. This type of alumina/tungsten cermet is approximately hm. cm. It has a solid resistance of 10o. The coefficient of thermal expansion in the temperature range from 0 to 90,000 °C is only 2 x 10-7/°C, which is lower than that of polycrystalline alumina.

One method for producing conductive alumina/tungsten cermets with very low tungsten content is to carefully size tungsten powder of 11 m average diameter, 99.95% purity, preferably having a spherical shape. It is mixed with alumina grains having an average diameter of 500 grains.

Submicron metal powders are used for more effective metallization of ceramic grains. In order to make maximum use of the metal powder, care must be taken to eliminate fine alumina jaw particles. It has also been found that it is beneficial to break up the tungsten chunks to prevent tungsten islets from becoming isolated. The mixture was then freely rolled for 60 minutes to deposit a uniform coating of tungsten powder over the grains. The metallized alumina grains are approximately spherical and have very good fluidity. The oxide/metal jaw grains obtained by rolling used in the production of the cermets of the present invention are preferably 770k9/c (11,000 psi)
It is formed by axial compression in a stainless steel mold under moderate pressure.

In order to avoid flaking of the metal deposited on the jaw grain, the metal-adhered jaw grain is flowed into the mold through a funnel. However, axial compression tends to crush the metal coated alumina grains resulting in an oblong network structure. In order to replace this, the molding method is 700 to k9/ground (10,0
00 to 20,000 psi) to achieve balanced compression of the rod. This method provides a more uniform structure, thus reducing the heterogeneity of physical properties. Rods pressed in this way additionally have a high wet strength with high processability and can be treated with a pre-hardening process using diamond-filled tools, which is normally required in the case of single layers of alumina. prefi
A good surface finish can be obtained without rming. The shaped material is sintered at 1,600 to 180,000 for 2 to 6 hours.

The high resistance to thermal shock of sintered cermets is demonstrated by the fact that large chunks of the material can be removed from furnaces above 1400° C. without cracking. In contrast, a similar mass of dense alumina will inevitably crack under the same conditions. From this point of view, the three-dimensional silk-like structure of the metal in the conductive monster of the present invention is
It is shown that the cermets of the present invention are endowed with much higher mechanical strength and durability than would be expected from the volume ratio of metal incorporated into the brittle ceramic lattice. FIG. 1 shows the conductive silk structure of tungsten in an alumina tungsten cermet containing tungsten at a volume ratio of 0.07.

FIG. 2, on the other hand, shows a non-conductive cermet containing tungsten in a volume ratio of 0.16. In the latter case, the tungsten powder, due to its special particle size and shape, does not metallize the alumina grains and therefore does not form a conductive silk-like structure. Figures 3 and 4 show the resistance changes associated with the size of alumina in refractory alumina, tungsten, and cermet. This is the case of .064. In each case, the horizontal axis is the alumina particle size (microns), and the vertical axis is the logarithmic resistance value. As shown in Figures 3 and 4, when the volume ratio of tungsten is both 0.049 and 0.064, the specific resistance value of the sintered cermet has a jaw grain size with an average diameter of 400 to 600 microns. It was found that the minimum value was found when . Figures 3 and 4
The results shown in the figure show that since the electrical resistance is mainly controlled by the initial size of the alumina grains, it is possible to obtain cermet materials ranging from insulators to conductors with virtually no difference in thermal expansion coefficient. It shows that it can be done. This property is
The present invention can be used in the construction of a cermet cap comprising a hybrid body for sealing an arc tube. '2
} Regarding Cermet Caps for Discharge Lamps One application of the materials of the present invention is the fabrication of end caps of conductive cermet for high pressure sodium lamps and other discharge lamps.

As shown in FIG. 5, in one example of such manufacturing, a rod made of pressed cermet of the present invention is processed into a top hat shape constituting the cap 1, and holes are drilled from the top and bottom of the cap.

In this case the upper and lower holes are on the same line and do not penetrate the cap. Next, a tungsten rod or wire 5a, 5b that fits snugly into this hole is inserted into it, and the
Sinter at 1800 oo for 2 hours. Upon sintering, the cermet undergoes approximately 20% linear shrinkage and forms an extremely strong mechanical bond with the tungsten rod. Approximately 140 assembled items
It can be taken out from a 0GC sintering furnace into an inert gas or reducing gas without causing cracks. The outer rod 5a is used for electrical connection with the outside, and the inner rod 5b is suitable for winding a filament and is used as a cathode of the lamp. The electrical conductivity of the cermet cap 1 maintains electrical continuity between the rods 5a and 5b. The electrode connections can be varied in various ways.

For example, as shown in FIG. 6, the rod 5a is made of cermet.
You can also insert it on the side of the top part of the calop. Electrical connection to the rod mother is accomplished by welding, soldering, or mechanically pinching the rod. Otherwise, the rod 5a may be omitted, for example by welding a rod or piece of nickel to the surface of the cap by high temperature welding using a ternary alloy of titanium-vanadium-zirconium. Still another method is shown in FIG.

This is a circular metal compression clip 6 that accommodates a protrusion of conductive cermet that is an integral part of the cap. The use of compression clips has the advantage that, under oxidative conditions, they can be easily welded or soldered to other metal parts used in the lamp. It can accommodate dimensional changes that occur during lamp operation, and can also be used as a rigid support in some constructions. When making a lamp according to any of these embodiments, a complete cermet cap with electrodes and electrical connection means is combined with a plug 4 integral with the cap and a translucent polycrystalline alumina tube 3.
A suitable ring-shaped sealing member 2, such as calcium-magnesium-aluminate, is placed between them and combined with the alumina tube.

The silk stand is placed in a convenient chamber for filling the arc tube with gas, heated in an inert atmosphere to a temperature above the softening point of the glass frit (approximately 1400 oo), and the tube is welded and sealed. FIG. 8 shows a 400 watt high pressure sodium lamp with an external jacket 7 and a military conductive end cap of the type shown in FIG. Owing to the good chemical compatibility of the alumina/tungsten end cap, this type of structure is also suitable for other types of discharge vessels, for example containing metal halides. The invention additionally provides a conductive cermet with an annular groove, which is more particularly used for sealing "coasters" or ceramic envelopes made of polycrystalline alumina.

Significant technical difficulties have been exposed in the sealing of "coaster" arc tubes in the construction of electrical discharge equipment.
One major problem is that the ends of the sealing "coaster" tubes develop cracks. Cracking becomes more severe as the diameter of the "coaster" tube increases. To solve this problem, expensive caps made of, for example, niobium have been provided, as disclosed in British Patents Nos. 1,361,225 and 1,398,425, but the present invention The object of the present invention is to provide a cap made of conductive cermet that can be satisfactorily used for sealing a "coaster" tube. Such cermet materials are of the type containing metal to volume ratios as low as 0.045 with oxide particles in the 400-800 micron range. This technique can also be directly applied to sealing polycrystalline alumina arc tubes when the cermet selection is less precise. One simple way to use these cermets in the fabrication of high pressure sodium lamps or metal halide lamps is to create a disk of cermet with an annular groove into which the end of the arc tube can be ironed, as shown in Figure 9A. It is to produce.

In the plan view of the cermet cap shown in FIG. 9B, the unshaded portion represents the annular groove. This method of sealing the end of the arc tube has several advantages. The cap used is simple in design, easy to machine and press, and the annular groove is effective in securing the end of the arc tube. Furthermore, in addition to the cross-section of the tube, the outer surface of the tube is also sealed, thereby increasing the leakage path. The sealing mechanism is simple and extremely strong due to the compressive stress applied to both ends of the ceramic envelope. The grooved conductive cermet "coaster" or polycrystalline alumina arc tube 11 of FIG. 9A is placed on top of the conventional glass arc tube 11. Welded and sealed with a frit (e.g. calcium-magnesium-aluminate). The glass frit is formed into a thin washer and either pre-sintered and placed in groove 13 (FIG. 9B) or pre-fused in an annular groove to facilitate sealing. Figure 10 shows two partially inserted tungsten or molybdenum rods 14 and 15. These are used as electrodes 14 and external electrical connection means 15, respectively. Other numbers in Figure 10 are Figures 9A and 9B.
The same numbers in the figure indicate the same parts. FIG. 11 shows another embodiment of a conductive cermet cap having protrusions for supporting an electrode and two rods serving as means for electrical connection with the outside.

This configuration, in which metal rods 14 and 15 are long, has several interesting features compared to the structure shown in Figures 9A and 9B. Firstly, the risk of damage when drilling the green cermet cap is reduced, and secondly, by increasing the distance between the metal rods 14 and 15, the cermet The electrical resistance is increased.
This parameter can therefore be adjusted to obtain a sufficient heating effect to modify the temperature of the cold spot, which is particularly useful for example in low power, high pressure sodium lamps.
An external projection 16 of small cross-sectional area is an integral part of the cap 10 and is used to further mechanically support the lamp. 12A and 12B have all the features of the embodiment of FIG.
7 and 18. FIG. This construction has the additional advantage of allowing a more even distribution of the pressure applied to the sealed area during operation of the lamp. FIG. 13 shows an example of a fully assembled discharge lamp using a grooved conductive cermet end cap. arc tube 11
is fitted with end caps and electrodes as previously described and is supported by a conductive wire 19 extending from the rod 15 and base 20 into the interior of the outer transparent jacket 21. Glue The problem of mismatching coefficients of thermal expansion between metal electrodes and ceramic arc tubes used in high-pressure discharge lamps for composite caps and tubes is addressed in accordance with aspects of the present invention by fabricating the end portions of two or more materials. be overcome by

In this case, the part bonded to the electrode is made of cermet, which has better mechanical strength and durability than alumina, and has a coefficient of thermal expansion that is more compatible with the electrode material than alumina. The portion that is in close contact with the wall of the arc tube is made of the same material as the arc tube or a cermet whose thermal expansion coefficient substantially matches that of the arc tube and which does not chemically react with the material filled in the arc tube. Although progressively expandable seals have been provided for some time, the fabrication of a single part with two or more parts made of different cermets or ceramics is new and requires We believe that, besides the direct purpose of sealing the electrodes, it opens up several new possibilities in the manufacture of lamps.

The very good flowability of metallized oxide grains, as well as the excellent workability of pressed compacts, can be exploited to produce objects of complex shapes.

Graded cermet parts of layered or nucleated structure are made by sequentially filling a mold with a series of metallized alumina grains of graded increasing metal content to produce a graded cermet part of about 770 k9/
11,000 psi). FIG. 14 shows a layered structure cap consisting of a conductive cermet layer 22, an intermediate cermet layer 23 and an alumina layer 24, with a tungsten electrode 25. FIG.

The advantage of this graded unit is that the alumina layer 24 can be welded and sealed to the alumina plug 26 and alumina tube 27 using a conventional glass frit, and the alumina layer can be welded to the tungsten electrode. This is not necessary, thus avoiding the risk of cracking at this interface. The tungsten legs of electrode 25 are secured by cermet layers 22 and 23 as described above. Cermet layer 22 is electrically conductive, and electrical connections thereto may be made by any of the methods previously described. This cermet is manufactured according to the first aspect of the invention. The intermediate cermet layer 23 is made of a cermet having a coefficient of thermal expansion between that of alumina and conductive cermet. More than one intermediate layer can be used if desired. 28 is a ring-shaped sealing member.

FIG. 15 shows a cored structure in which the core 29 is made of conductive cermet and the periphery 30 of the core is made of alumina. As the metal content decreases, the coefficient of thermal expansion of the cermet approaches that of alumina, so the material around the core 30 may be a cermet with a small volume ratio of metal. Due to the new technology used to produce the conductive cermet according to the first aspect of the invention, in which the metal content is low and is distributed in a continuous three-dimensional network, conductive cermets and alumina are used together. sintered into a completely monolithic layered or nucleated structure with no intermediate cermet in between.
Figure 19 shows a conductive alumina/tungsten top.
Part of such a layered structure is shown, consisting of cermet (the genus appears as a bright mesh) with the lower part consisting of regular alumina ceramic. The design of the cap can also be modified to include multiple electrodes, for example with an auxiliary starting electrode.

When one cap includes multiple electrodes, the individual electrodes are separated by an insulating material. In certain applications, it is advantageous to construct discharge lamps in ceramic arc tubes (ie, discharge tubes without an outer jacket) that can be brought into contact with air. This is not possible with known structures. This is because the outer metal portion of the cap/electrode assembly will be used at a temperature higher than its oxidation temperature. For such tubes, the 16th
A cap is made consisting of a ceramic body 32 with a long conductive cermet core 31 as shown. An electrode 33 is attached to the inner end of the conductive cermet core 31, and the outer end protrudes from the ceramic body 32. In practice,
The cermet core 31 is encased in ceramic and is only exposed at a distance from the lamp where the temperature is below the oxidation temperature of the metal contained in the cermet. Electrical connection thereto can be achieved by any of the methods disclosed in the previous description. The present invention also utilizes a hybrid cermet cap to seal a closed-ended ceramic envelope made of monocrystalline or polycrystalline alumina. FIG. 17 shows an insulating cermet 34 and a conductive cermet 3 having substantially the same coefficient of thermal expansion manufactured based on the results shown in FIGS. 3 and 4.
5 shows a cross-section of an embodiment of this kind according to the invention using 5. For example, an insulating, conductive alumina/tungsten cermet can be produced using alumina grains with a diameter of 50 microns or less, and alumina/tungsten cermets with a diameter of A conductive cermet is obtained using 500 micron alumina grains. The ceramic envelope 36 is cast into the groove and welded and sealed with a conventional glass frit 12.

The insulating cermet 34 has two step-shaped holes, and a conductive cermet 35 having a shape that matches the holes in which the metal rods 14 and 15 are partially embedded is iron-bonded therein, and a glass frit is inserted into the insulating cermet 34. Sealed at 12. Alternatively, the composite cap may be formed from an insulating cermet and a conductive cermet, which is then phosphorized from a green state into an integral solid. Although the absence of a cermet tube extending from the cap is sufficient for assembling high pressure sodium lamps, by providing a molybdenum-tungsten or cermet tube 37, the cap can also be used for assembling metal highland lamps. . A cermet tube 37 extending from the cap according to the present invention is made as an integral part of the cermet cap so as to be suitable for introducing metal halide material and sealing the device. The tube is closed by inserting an alumina or cermet plug 38 and welded sealed with a glass frit 12. To prevent volatile components from evaporating during sealing, the glass frit is locally melted at the end of the elongated cermet tube. Although the conductive cermet, hybrid cap and tube are both particularly useful in high pressure discharge tubes using ceramic arc tubes, the invention also applies to ceramic tubes or ceramic tubes, such as incandescent lamps or tungsten/halogen lamps. It can be used with any device that uses an outer envelope.

For example, in lamps that require a precisely focused filament, such as in automobiles, movie projectors, or flashlights, when some types of flanged caps are used, the flange is fixed to the cap or the cap is fixed to the lamp. It is common to attach the cap and flange to the finished lamp before viewing and positioning the filament relative to the reference surface of the flange.

This is the so-called prefocus structure.
This is called sed construction. According to our invention, as shown in FIG. 18, the cap with locating flange 40 is made of non-conductive cermet or ceramic, but includes a portion of conductive cermet 41 therein.

A conducting wire 42 is inserted into the conductive cermet 41 before sintering the cap. After freezing, the filament or filaments are precisely positioned relative to the reference surface and secured to the conductor wire 42. A light-transparent transparent cover 43 is then placed over the cap (preferably in the annular groove 44) and either welded directly to the substrate or sealed via an indirect material such as a glass frit 45. . The lamp is then evacuated in the usual manner through a transparent cover or exhaust tube (not shown) attached to the base.
Filled with gas. Electrical connection is conductive cermet 41
It can be done directly on the outer surface of the lamp or by any of the modification techniques described for discharge lamps.
This method simplifies the fabrication of pre-focused lamps and is suitable for designs with one or more filaments, regardless of whether pre-focusing is easy or not. It can be applied. In other constructions, such conductor wires are omitted and the elongated filament legs are inserted directly into the conductive cermet.

Desirably, the legs can be reinforced with helical tungsten coils. This technique is already known in the production of certain tungsten/halogen lamps. Although the invention has been described in the context of discharge tubes and the like having electrodes that do not extend through the cap, these materials and structures may be advantageously used in some cases with electrodes that extend through the cap.

For example, even if the electrical conductivity of the cermet according to the invention is not exploited, the excellent mechanical strength of the cermet is useful. Application of the layered structure of cermet and ceramic is further shown in FIGS. 20 and 21.
It can be extended to the production of sitcaps.

For example, FIG. 20 shows an alumina arc tube 51 having a cermet distal end 50 that can act as a heat shield to control the temperature of the arc's cold spot. FIG. 21 shows an alumina tube 53 in which a cermet filament 52 is roughly inlaid in the longitudinal direction of the tube.
gaid). [4] Other applications The conductive and insulating cermets of the present invention can be used to form various structures other than end caps of discharge tubes.

For example, insulating cermets have chemical compatibility for supporting sagging tungsten filaments, for laying wires, e.g. tungsten or molybdenum conductors, and even in tungsten/halogen lamps. It can be used as a carrier for getter materials. This is possible because the cermet of the present invention can be bonded onto several tungsten or molybdenum wires or rods without cracking. Conductor wires and electrodes made of metals other than tungsten can also be used as long as they are heat-resistant and can withstand the temperatures in the furnace.

The preferred furnace gas is hydrogen, but may also be a vacuum or an inert gas under constant conditions. The cermet of the present invention can be bonded to a variety of thermal expansion matched glasses, such as shelf silicate glass, with or without the use of a glass frit seal.

[Brief explanation of drawings]

Figure 1 shows a conductive alumina/tungsten film according to the present invention.
Enlarged view of cermet (60x), Figure 2 is an enlarged view similar to a normal conductive cermet, Figure 3 is a volume ratio of 0.049
A graph showing the resistance change of a competitively bonded alumina tungsten cermet made of tungsten and grain-sized alumina.
Figure 4 is a graph showing resistance changes with the size of alumina grains of a tungsten cermet containing a tungsten volume ratio of 0.064, and Figures 5 to 8.
The figure is a partial sectional view showing the structure of the end cap of the arc tube according to the present invention, and Figures 9A and 9B are side sectional views and cross-sectional views, respectively, of the arc tube iron-bonded to the grooves of the cermet grooved cap. 10 and 11 are cross-sectional views showing an arc tube ferrobonded to one embodiment of a grooved conductive cermet cap, and FIGS. 12A and 12B are cross-sectional views showing two identical D circular shapes. 13 side and cross-sectional views, respectively, of an arc tube iron-bonded to a conductive cermet cap having grooves of
The figure shows a partial cross-section of an embodiment of a ceramic discharge lamp using two grooved cermet caps, and FIGS. 14 to 18 show cross-sections of end caps made of a mixture incorporating cermet parts according to the invention. Figure 19 is an enlarged view of an integral structure containing a conductive cermet layer and a salamic (10 Kanon), Figures 20 and 21 respectively show two types of arc tubes made of the mixture according to the invention. FIG. 2 is a schematic cross-sectional view and a perspective view. DESCRIPTION OF SYMBOLS 1... Cap, 3... Alumina tube, 10... Cermet cap, 11... Arc tube, 22... Conductive cermet layer, 23... Intermediate cermet layer, 24... ...Alumina layer, 25...Tungsten electrode, 27...Alumina tube, 29...
Cermet core, 32...Ceramic body, 33...
...Electrode, 34...Insulating cermet, 35...
... Conductive cermet, 36 ... Ceramic outer envelope, 41 ... Conductive cermet, 42 ...
... wire, 51 ... alumina arc tube,
52... Cermet striations. (G.7 (G.2 (o3 (GS (o・4 〃G.6 (G.A(6.8 (6.9A) G.98 柤G.YutsukeG〃 (G.J2A Row 6. 728 (6.73 〃G. Buddha (c.6 (0.ノ0 ri6.〃) (6.78 (G. meta〃G.20 (6.2〆

Claims (1)

[Claims] 1. Constituting a conductive network extending over the entire area of the cermet,
consisting of granules of refractory oxide surrounded by a thin layer of at least one metal selected from the group consisting of W, Mo, Cr, Fe, Ni, the volume ratio of the metal being between 0.045 and 0.2; A conductive cermet characterized by the following. 2 The refractory oxide is Al, Mg, Be, Y, Hf,
The conductive cermet according to claim 1, which is one or more oxides selected from the group consisting of oxides of Zr and Th. 3 Constructs a conductive network that spreads over the entire area of the cermet,
Consisting of granules of refractory oxide surrounded by a thin layer of at least one metal selected from the group consisting of W, Mo, Cr, Fe, Ni, the volume ratio of the metal being 0.045 to 0.2
A method for producing a conductive cermet, comprising: a fine powder of the above metal having an average particle size of 12 microns or less; and the above refractory oxide granules having an average particle size of 50 to 800 microns; 1. A method for producing a conductive cermet, comprising rolling the cermet until it is uniformly coated with fine powder, compressing the coated granules to form an aggregate, and sintering the aggregate. 4 The refractory oxide is Al, Mg, Be, Y, Hf,
4. The method for producing a conductive cermet according to claim 3, wherein the conductive cermet is one or more oxides selected from the group consisting of oxides of Zr and Th. 5 The coated granules weigh 700 to 1400 kg/c
4. The method of manufacturing a conductive cermet according to claim 3, wherein the conductive cermet is compressed under a pressure of m^2 (10,000 to 20,000 psi). 6. The method for manufacturing a conductive cermet according to claim 3, wherein the aggregate is sintered at 1600 to 1800°C.