Title of Invention

"AN IMPREGNANT CATHODE COMPOSITION AND PROCESS FOR PREPARING THE SAME"

Abstract The present invention relates to an impregnant cathode composition to improve emission performance of cathode, comprising 99-95 wt. % aluminates of alkaline earth metals doped with 1.0-5.0 % by weight lithium, and a process of preparing the said impregnated cathode composition and its use for manufacturing electron tube.
Full Text Field of Invention
The present invention relates to an impregnant cathode composition and process for preparing the same. More particularly, the invention relates to manufacturing of thermoionic electron tubes, particularly at very high frequencies, and their performance as related to their thermoionic cathodes.
Background of the Invention/Prior Art
The power generated by electron tubes at very high microwave frequencies has in many sets of operational parameters been limited by the thermoionic emission density, which can be obtained from the cathode. In tubes designed for continuous-wave operation, the most suitable cathodes are quite different from the oxide-coated cathode usually used for short-pulse operation, and the requirements are much more severe.
The exact scaling laws for tube capability are not easily defined, but some power-laws are easily derived. For example, in a linear-beam tube with fixed values of perveance and area convergence of the electron beam (which are both limited by design considerations) the maximum microwave power output is proportional to the fifth power of the current density. Therefore, doubling the emissivity of the cathode will permit a 32-fold increase in power in the frequency range where emission is the limiting factor.
Cathode, being the source of the electron is the most critical component and only active component of vacuum electronic devices like microwave tubes, X-ray tubes, particle accelerators etc. With the need to go to higher and higher powers, there has been a consistent demand for cathodes with higher emission density and lower operating temperatures. These cathodes also require good life in adverse operating conditions like ion bombardment etc. Most of the present day vacuum electronic devices use impregnated dispenser type of thermoionic cathodes. Thermoionic cathodes have long been known comprising a metal matrix with pores containing active oxide material, particularly barium oxide. Such cathodes have been made by pressing mixtures of nickel powder and alkaline earth carbonates ("mush" cathodes).
These cathodes are heated in the electronic tube in which they are used, to break down the carbonates into oxides, with evolution of much carbon dioxide and consequent difficulty in evacuating the tube. Mush cathodes have given somewhat improved continuous emission at higher current densities than the traditional oxide-coated cathode. At their operating temperature the vapor pressure of nickel is marginally high.
Dispenser cathodes are basically porous tungsten pellets impregnated with barium calcium aluminates and indirectly heated using potted heater structures. These cathode (type B as they are called) surfaces when coated with a film of osmium, osmium-ruthenium or iridium are found to give enhanced emission at the same operating temperature. Scientists have achieved current density up to 15 A/cm2 form M type cathodes and typical current density of B type cathodes is - 5 A/cm2. Since they can be operated at a lower temperature (normally 50 to 100 C) than the B type cathodes the life expectancy is higher.
For cathodes delivering emission currents of one ampere or more per square centimeter continuously, it has been found desirable to provide a continuous matrix of metal to carry the high currents.
The dispenser "L" cathode used a matrix of tungsten particles sintered together. In a cavity inside the matrix was a charge of barium oxide (formed by breaking down barium carbonate). In operation, barium oxide and free barium reduced by reaction of the oxide with tungsten diffuse to the surface of the porous tungsten body and activate it for thermoionic emission. The "L" cathode has been of only limited use, due to some inherent difficulties. The enormous exposed surface of the porous tungsten and the tortuous diffusion paths through its pores, result in an evolution of gas from the oxide charge and from the porous body itself which takes a very long time to pump out. Furthermore, the operating temperature of the "L" cathode is high, e.g. over 1100° Celsius. This temperature makes the reliability and life of insulated heaters become poor. Numerous attempts have been made to impregnate barium oxide directly into the
pores of a porous metallic matrix. It was found that molten barium oxide reacted with the tungsten and poisoned the cathode.
An Improved impregnated cathode is described in U.S. Pat. No. 2,700,000 issued to R. Levi et al on Jan. 18, 1955. This patent teaches that if the barium oxide is combined with aluminum oxide to form barium alumlnates the molten mixed oxide can be impregnated into a tungsten matrix without reaction with the tungsten to form the harmful barium tungstates.
U.S. Pat. No. 3,201.639 issued Aug. 17, 1965 to R. Levi made the first Impregnated cathode with 5:0:2 impregnant composition on porous tungsten matrix. With these cathodes emission of 1-3 A/cm2 was achieved with considerably long life .He further found that addition of the oxide of a second alkaline earth element such as calcium improves the emission qualities of the impregnated cathode. The cathode was called B-Type with the Impregnant composition ratio 5:3:2 (BaO:CaO:Al203). Typically B-type cathodes gave about 5 A/cm2 current density at operating temperature of 1050°C. Zalm & Van Stratum [2] Invented M-type dispenser cathodes in 1966. They converted a B-type dispenser cathode in to M-type cathode by coating a high work function metal such as Osmium on the emission surface. By this process, there was an Increase in electron emission density by about three times. Some drawbacks that affect the life & performance of M-type cathodes are damage of emission enhancing metal layer due to ion bombardment and diffusion of tungsten in to the metal film. This results in gradual reduction of emission during the course of its life.
Different groups across the world developed mixed metal matrix cathodes to overcome the drawbacks of M-type dispenser cathodes. U.S. Pat. No.4, 165,473 issued to L. Falce on August 21, 1979 teaches that thermionic emission of W- Ir (Tungsten-Indium) mixed metal matrix cathode is Improved compared to a tungsten matrix. Barium evaporation is reduce to performance of W-lr cathodes impregnated with barium calcium alumlnates is slightly better than B-type cathodes but it is well below the performance of M-type dispenser cathode. This was attributed to lower barium evolution from the W-lr cathodes in comparison to M cathodes. B.K.Vancil et al [5]
ascribed this to lower reactivity of the W-lr alloy phases with the impregnant material. This relative paucity of barium has been observed in the results of both time-of-flight mass spectroscopy RGA and Auger Surface analyses. This implies that the tungsten solid solution phase was critical to provision of an adequate level of reactivity towards the impregnant material as a means of assuring sufficient barium supply in W-lr cathodes, although its reactivity is indicated to be somewhat lower than that of pure tungsten. However, as noted above, work function of the £ phase was lower than that observed for pure tungsten or the W phase, if adequate barium coverage was achieved.
Russian patent No.2066892 issued to V. A. Smimov & I. E. Crasnitscaya in Sep, 1993 teaches that addition of lithium oxide to impregnant composition consisting three moles of barium oxide, 0.5 moles of calcium oxide and 1 mole of aluminum oxide reduce the melting temperature of the impregnant composition. The work function of the porous tungsten cathodes impregnated with this impregnant composition, around 2+ (5±1)*(T -1300)*10-4 eV which gives 2 eV at 1300°C.
W-lr mixed metal matrix type cathodes were invented in 1969 could not replace the M type cathodes in microwave tubes. Even today more than 90% of the microwave tubes use M type cathodes. Though W-lr cathodes are more resistant to ion bombardment, their emission density is lower than the M type cathodes. The main objective of this invention is to improve the emission performance of W -Ir mixed matrix cathodes by using a suitable impregnant composition. With this invention it is possible to have low cost, long life mixed metal matrix dispenser cathodes with higher emission densities and capable of working in harsh ion bombardment conditions of CW tubes.
The generic process of development of W- Ir cathodes is available in the literature. However there are some inherent problems associated with these cathodes, stopping their full scale use in microwave tubes. One of the major problems is lesser evolution rate of barium and another one is emission non-uniformity. These limitations have been well documented in the literature [vancil, shroff]. In this present invention we
modified some of the process parameters in order to overcome these difficulties. The
details of modifications are given below.
Porous pellets of dispenser cathodes are fabricated using powder metallurgy process
due to refractory nature of materials involved. Proper choice of particle sizes is very
much essential to attain required porosity with uniform pore density along with pore
connectivity. In the case of W -Ir mixed metal matrix cathodes these particle sizes
playa major role due to presence of two phase structure, namely tungsten solid
solution phase and E phase. B.K. Vancil et al pointed out that lesser evolution of
barium from W-lr cathodes is due to lesser reactivity tungsten solid solution phase and
no reactivity of E phase with barium calcium aluminates. However £ phase is
responsible for increased emission due to its hexagonal close packed structure.
Summary Of Invention
The objective of invention is to develop dispenser cathodes without substantial increase in the production cost of the cathodes with enhanced emission performance. Accordingly, W-Ir mixed metal matrix dispenser cathodes when impregnated with lithium oxide doped 5:3:2 impregnant composition showed considerable improvement in the emission performance.
Objects of the Invention
An object of the invention is to provide an impregnant composition to enhance the
emissive efficacy of dispenser cathode with substantially increased electron emission
density.
Another of the invention is to provide a dispenser cathode with substantially low
work function.
Still another object is to provide a dispenser cathode having substantially increased
life.
Yet another object of the invention is to provide an improved thermoionic cathode
capable of emitting higher current density than previously available cathodes.
Yet another object is to provide a cathode with long life and low rate of evaporation of active material.
Yet another object is to provide a cathode, which is resistant to degradation by arcs and ion bombardment.
Brief Description of the Drawings/Figures
Figure 1. Shows the cross sectional diagram of the electron tube.
Figure 2. Shows the schematic diagram of the emission characterization of W-lr
dispenser cathodes.
Figure 3. Shows the emission performance of W-lr mixed metal matrix dispenser
cathodes when impregnated with lithium oxide doped 5:3:2 impregnant composition.
Figure 4, Shows the variation of work function with temperature for a W-lr cathode
with lithium Oxide doped impregnant mixture.
Figure 5. Shows the performance of W-lr dispenser cathodes with and without lithium
oxide doping.
Detailed Description of the Invention
According to first embodiment of the present invention an impregnant composition to
improve emission performance of cathode comprising 99-95 wt. % aluminates of
alkaline earth aluminates doped with 1.0-5.0 % (by weight) lithium.
According to second embodiment of the present invention alkaline earth metals are
calcium and barium.
According to third embodiment of the present invention percentage of lithium is 3% by
weight.
According to one aspect of the present invention a process for preparing impregnated
cathode, said process comprising the steps:
(a) mixing 4-6 moles of barium carbonate, 1-3 moles of calcium carbonates and 1-3 moles of aluminum oxide to obtain a mix,
(b) adding 1-5 % by wt of lithium carbonate to the mix of step (a) to obtain pre-impregnant composition,
(c) fixing the pre-impregnant composition of step (b) at a temperature in the range of 1100 to 1500°C for a period in the range of 7-8 hours to obtain impregnant composition,
(d) separately mixing a first metal and a second metal, wherein first metal selected from a group comprising of tungsten and molybdenum and second metal is selected form a group consisting of iridium, osmium, ruthenium and rhenium in a ratio in the range of 70-90 : 30 to 10 to obtain a porous mix,
(e) compacting the porous mix of step (d) under a pressure in the range of 15,000 - 30,000 psi to obtain a mixed metal pallet,
(f) sintering the pallet of step (e) at a temperature in the range of 1600 to 1800°C to obtain mixed metal button, and
(g) impregnating the mixed metal buttons of step (f) with impregnated mix of step (c) at a temperature in the range of 1400 - 1800°C to obtain impregnated cathode.
According to another aspect of the present invention a process for preparing
impregnated cathode, wherein the first metal is selected from a group of metals
having a particle size in the range of 5-8 microns.
According to yet another aspect of the present invention a process for preparing
impregnated cathode wherein the second metal is selected from a group of metals
having a particle size is less than 45 microns.
According to still another aspect of the present invention a process for preparing
impregnated cathode wherein firing of impregnant composition and impregnation of
porous buttons is done under H2 atmosphere.
According to still another aspect of the present invention a cathode comprising a
matrix of metals; said matrix consisting of a first metal selected from a group
comprising tungsten and molybdenum and a second metal selected from a group
comprising iridium, osmium, ruthenium and rhenium along with impregnant
composition.
According to still another aspect of the present invention a cathode wherein porosity
throughout the volume of said matrix comprises approximately 18% to 22% of the
volume thereof.
According to still another aspect of the present invention a cathode in which said
second metal of iridium is about 20%) by weight of the said matrix.
According to still another aspect of the present invention a cathode as wherein said
second metal is iridium and in which the amount thereof consists of about 10% to 30
% by weight of said matrix.
According to still another aspect of the present invention an electron tube comprising
a cathode comprising a matrix of metals; said matrix consisting of a first metal
selected from a group comprising tungsten and molybdenum and a second metal
selected from a group comprising iridium, osmium, ruthenium and rhenium along with
impregnant composition. The button 1 is supported by a molybdenum cup 3. Heater 5
made using Tungeston-Rhethium (W-Re) wire and it is housed in the molybdenum
inner sleeve 4 and an outer sleeve 6 made of Moly-Rhenium is used as a mechanical
support as well as thermal heat shield. Heater 5 is unpotted and the button is heated
through radiation.
Detailed Description of the Invention
Basic Description of the dispenser cathodes
Figure 1 shows the schematic diagram of the electron tube. The W-lr dispenser cathode consists of a porous mixed metal button 1 into which a mixture 2 of barium calcium aluminates doped with lithium oxide is impregnated. The button is supported by a molybdenum cup 3. Heater 5 is made using Tungeston-Rhethium (W-Re) wire and it is housed in the molybdenum inner sleeve 4 and an outer sleeve 6 made of
Moly-Rhenium is used as a mechanical support as well as thermal heat shield. Heater 5 is unpotted and the button is heated through radiation.
Process of Making Porous Buttons 1
Following steps were involved in the making of porous matrix 1: -
(a) High purity tungsten (W) powders with particle size distribution with particle size around 5-8 microns and iridium (Ir) powder of -325 mesh ( (b)This mixture of step (a) containing W powders and iridium powder were pressed into pallets using high pressure in the range of 15,000-30,000 Psi under inert conditions.
(c) Pressed pallets of step (b) were sintered at temperature in the range of
1600- 1850°C for one hour to obtain porous W-lr button.
(d) This temperature schedule was optimized based on the phase diagram
of W-lr.
(e) Optimization of time of sintering was done to achieve final porosity of
20 ± 2%.
Process of Making Impregnation Mix 2
Lithium doped barium calcium aluminates are prepared using 1.0-5.0 %(by weight) of lithium oxide (LizO) with 5 moles of barium oxide (BaO), 3 moles of calcium oxide (CaO) and 2 moles aluminum oxide (AI2O3).
(TABLE REMOVED)
To this mixture 3% lithium carbonate (Li2CO3) is added (1482*3/100=44.48gms).
The total weight of the mixture after adding the lithium carbonate is 1527.34
grams.
The weight percentages of BaC03, CaC03, Li2C03 and A1203 before firing in air
furnace are as follows
(TABLE REMOVED)
Afterward the mixture is calcined in air furnace at around 1100°C for 8-10 Hrs. All the carbonates decompose into oxides and a reduction in weight is observed.
(FORMULA REMOVED)
After calcinations the weight and weight percentage of BaO, CaO, AI2O3, UiO^ are as follows:
(TABLE REMOVED)
Weight loss observed during the calcinations is 24.84%.
Atomic weights of various elements and compounds taken for calculation
(TABLE REMOVED)
Process of Impregnation
W-lr cathode pallets were impregnated with these lithium oxide doped barium calcium aluminates around 1600°C in hydrogen atmosphere. The weight gain of the cathode pallets was found to be 5,5 % as expected for >90% impregnation MM type cathodes using 1.4 mm diameter W-lr pallets were fabricated using these impregnated pallets.
The above examples illustrate structure and fabrication methods for particular cathodes used in the invention. It will be readily obvious to those skilled in the art that many other variations and embodiments are possible. For example, It is known that the elements osmium, ruthenium and rhenium all have properties very similar to iridium. At least the first two of these elements, or alloys thereof, may be substituted for the described pure Iridium. Also tungsten can be replaced by molybdenum. Many formulations of alkaline earth aluminates have been found usable In Impregnated cathodes, depending upon the particular properties desired.
Test and Evaluation of Cathodes
Emission density of a cathode is defined as the emission drawn from unit surface area of the cathode. Unit is Al cm2. For determining the emission density of a cathode, cathode is tested in closely spaced diode configuration. Cathode is heated 1050°C and voltage is applied between the anode and the cathode. Anode current as a function of anode-cathode voltage is recorded. For lower voltages « 100 V typically for close
spaced diodes) cathode operates in space charge region and Child's Law (l=kV2/3) is applicable in this region. In this space charge limited region we will be draw'ing lesser number of electrons than emission capability of the cathode. When the voltage is more than 1500 V, all the electrons emitted by the cathode will collected by the anode. This region is called saturation region.
The graph (figure3) showing the Emission performance of W-lr cathode impregnated with lithium oxide doped 5:3:2 impregnant composition implies the uniform emission in the space charge region and the emission increases in the temperature limited region with the increase of temperature. The Zero field emission current achieved at 10750C is 32 Alcm2. The graph (figure 4) showing the Variation of Work Function with Temperature for lithium oxide doped W-lr Mm type cathode gives the optimum operating temperature with the lowest work function. The graph (figure 5) showing the Performance of W -Ir dispenser cathodes 'with' and 'without' lithium oxide doping at 1050°C implies the drastic improvement of emission with the lithium doped W-lr MM type cathode.
For emission characterization MM type cathodes were sealed in close spaced diode configuration in glass bulbs. For testing of MM type cathode, glass bulbs is mounted in a UHV station and evacuated to (FORMULA REMOVED)
After activation of the cathode in close spaced diode configuration the anode degassing has been carried out by electron bombardment from the cathode. A DC voltage of ~ 130 V has been given to the anode for acceleration of electron. After
completely degassing the anode, pulse voltage is applied between that anode and the cathode. The schematic diagram of emission characterization is shown in figure 2. Heater power supply is floated using an isolation transformer. High voltage pulse is applied between the anode and the cathode. The temperature of the cathode was measured using a disappearing filament pyrometer. Typical emission characterization results are shown in figure 3. Fugure 3 shows available emission current density in amperes per square centimeters vs square root of anode voltage for different set of temperatures. Zero field emission density (Jo) of cathode at a given temperature is an accepted parameter for characterizing dispenser cathodes. Zero field emission density can be extrapolated from the V -I characteristics plotted on a semi -logarithmic graph sheet with V on x-axis and current density/current on the y axis. Intercept on the y axis for the line drawn tangential to the V-l curve in the temperature limited region gives the zero field emission density. From Richardson-
Dushman equation Jo=120T 6*" average work function will be calculated at the
operating temperature.
Average work function is a measure of the quality of the cathode. A lower work function cathode will give higher emission. However, this average work function is not a constant but changes with the temperature. Formation of Ba-0 dipole layer on the surface of the dispenser cathode is essential for the electron emission from them. At lower temperature, rate of supply of barium from bulk of the cathode is less and the work function of the cathode is high. At the optimum temperature of operation of dispenser cathode, the supply and desorption of the barium are balanced and work function will be lowest. As shown in figure 4, the lowest work function value for the W-lr dispenser cathode impregnated with lithium oxide doped impregnant 2 mix, is 1.80 eV. It is lower than typical B-type cathode value at least by 0.3eV and by 0.1eV than M type cathode. Figure 5 shows the available emission current density in amperes per square centimeters vs square root of anode voltage. The performance of W-lr cathode with lithium oxide doped impregnant 2 mix vis-a-vis the performance of
W-lr cathode with 5:3:2 impregnant composition. For realization of both the cathodes, W-lr pallets from the same batch were used and both the cathodes were tested in similar test conditions. From figure 5, improved performance of lithium-doped cathodes can be seen. One of the lithium doped W-lr cathodes kept on life test with DC loading of 2 A/cm2 has been working for last 2500 hours and still continuing with out any degradation of emission.
In present invention cathodes, are chosen larger particle size for Iridium (- 45 microns) and smaller particle size for tungsten (~ 4 microns). Smaller particle size of tungsten particles provides more surface area for enhanced reaction with impregnant composition and hence more barium evolution. Disparity in the particle sizes of two powders causes a skeletal structure of smaller tungsten particles studded with larger particles of Iridium. W-lr £ phase will now be localized only to the grain boundaries. Present invention is able to solve the problem of barium evolution in W-lr cathodes with larger particles of Iridium. Present invention also developed a special fixture for mixing of two powders in a roller mill. Typical mixing time is about 48 Hrs. In order to reduce inter particle friction; organic lubricant like PMAAA, PVA etc are used. This lubrication process helped us in achieving good compaction and porosity.
Present invention improved the method Smirnov in his patent suggesting that lithium oxide can be added to barium calcium aluminates, by adding lithium carbonate to carbonates of barium and calcium and aluminum oxide. Present invention uses wet grinding technique for thorough mixing of all carbonates. This enhances the uniform distribution of lithium with in the impregnant composition. Then the mixture is calcined to convert carbonates into aluminates at 1000 - 1 100°C for 8 - 12 hours in an air furnace.
With these novel modifications the generic process of developing W-lr cathodes with lithium oxide doped impregnant composition, gives reliable and high emission density mixed metal matrix dispenser cathodes for use in vacuum electron devices. The working principle of dispenser cathodes is as follows.
- For getting electron emission from dispenser cathodes, they have to be heated to 1050°C in ultra high vacuum ( - When heated the impregnant (barium calcium aluminates doped with lithium oxide) reacts with tungsten in the pores releasing barium
- Barium travels through the pores to the surface by Knudsen flow

- At the surface barium migrates to cover the surface up to a monolayer
- The coverage and metal substrate composition determine the work function
- electrons are extracted from the metal surface whose work function has been lowered by activating metallic barium film
Working of the W-lr mixed metal matrix is also similar but Tungsten solid solution will participate in the reaction with barium calcium aluminates. Presence of £ phase on the surface will enhance the emission.
Optimization of Pressure:
According to metallurgical scenario, mixing of powders will create interparticle friction which leads to larger pores. The requirement is only small pores in larger numbers. Organic material like PMMA, PV A etc has been added at the time of mixing as a lubricant to achieve a uniform green density. Pressing has been performed in a uniaxial press at 20,000 psi, comparatively lower pressure to avoid interparticle friction.
Optimization of sintering time and temperature:
Sintering process is a very delicate process. During sintering the iridium partially alloys with the tungsten. If it is over sintered to get a lot of alloying, the emission is often poor. If the sintering is held to be minimum, the emission is initially good, but inter diffusion of iridium and tungsten occurs at operating temperature to form unreactive alloy. This in turn causes the barium supply to the surface to fall off with a resultant decay in emission. Also, shrinkage of the cathode button can take place with
the distortion of the emitting surface. Sintering time and temperature is optimized to carry out the sintering in the dry H2 atmosphere at 17500C for half an hour to form a reactive alloy to produce a good emission from the emissive surface.
The aforementioned embodiments are merely examples to illustrate the versatility of the invention. The true scope of the invention is intended to be limited only by the following claims and their legal equivalents.








WE CLAIM
1. An impregnant cathode composition to improve emission performance of cathode
comprising 99-95 wt. % aluminates of alkaline earth metals such as calcium and
barium, doped with 1.0-5.0 % by weight lithium, and
a matrix of metals, whereby the said matrix consisting of a first metal selected from a group comprising tungsten and molybdenum and a second metal selected from a group comprising iridium, osmium, ruthenium and rhenium.
2. An impregnant cathode composition as claimed in claim 1, wherein the lithium is preferably 3% by weight.
3. A process for preparing an impregnant cathode composition as claimed in claim 1, said process comprising the steps:

a) mixing 4-6 moles of barium carbonate, 1-3 moles of calcium carbonates and 1- 3 moles of aluminium oxide to obtain a mix,
b) adding 1-5% by wt of lithium carbonate to the mix of step (a) to obtain pre-impregnant composition,
c) fixing the pre-impregnant composition of step (b) at a temperature in the range of 1100°C to 1500°C for a period in the range of 7-8 hours to obtain impregnant composition,
d) separately mixing a first metal and a second metal, wherein first metal selected from a group comprising of tungsten and molybdenum and second metal is elected from a group consisting of iridium, osmium, ruthenium and rhenium in a ratio in the range of 70-90 : 30 to 10 to obtain a porous mix,
e) compacting the porous mix of step (d) under a pressure in the range of 15,000 -30,000 psi to obtain a mixed metal pallet,
f) sintering the pallet of step (e) at a temperature in the range of 1600 to 1800°C to obtain mixed metal button, and
g) impregnating the mixed metal buttons of step (f) with impregnated composition of step (c) at a temperature in the range of 1400 - 1800°C to obtain impregnated cathode.

4. The process as claimed in claim 3 wherein the first metal and second metal is tungsten and iridium respectively.
5. The process as claimed in claim 3, wherein impregnated composition in step (c) is fixed under H2 atmosphere.
6. The process as claimed in claim 3, wherein in step (f) mixed metal buttons are impregnated under H2 atmosphere.
7. The process as claimed in claim 3, wherein said percentage of Ir is iridium is 20% by weight of the said matrix.
8. An impregnated cathode composition as claimed in claim 1 or 3, is use for manufacturing the electron tube.

Documents:

3386-del-2005-Abstract-(03-08-2011).pdf

3386-DEL-2005-Abstract-(10-01-2011).pdf

3386-DEL-2005-Abstract-(25-05-2011).pdf

3386-del-2005-abstract.pdf

3386-del-2005-Claims-(03-08-2011).pdf

3386-DEL-2005-Claims-(10-01-2011).pdf

3386-DEL-2005-Claims-(25-05-2011).pdf

3386-del-2005-claims.pdf

3386-del-2005-Correspondence Others-(03-08-2011).pdf

3386-DEL-2005-Correspondence Others-(25-05-2011).pdf

3386-DEL-2005-Correspondence-Others-(10-01-2011).pdf

3386-del-2005-correspondence-others.pdf

3386-del-2005-Description (Complete)-(03-08-2011).pdf

3386-del-2005-description (complete).pdf

3386-del-2005-drawings.pdf

3386-del-2005-Form-1-(03-08-2011).pdf

3386-del-2005-form-1.pdf

3386-del-2005-form-18.pdf

3386-del-2005-Form-2-(03-08-2011).pdf

3386-del-2005-form-2.pdf

3386-del-2005-form-26.pdf

3386-del-2005-form-3.pdf

3386-del-2005-form-5.pdf


Patent Number 249485
Indian Patent Application Number 3386/DEL/2005
PG Journal Number 43/2011
Publication Date 28-Oct-2011
Grant Date 21-Oct-2011
Date of Filing 16-Dec-2005
Name of Patentee DEFENCE RESEARCH DEVELOPMENT ORGANIZATION
Applicant Address MINISTRY OF DEFENCE, GOVERNMENT OF INDIA, WEST BLOCK VIII, WING-1, SECTOR-1, R.K. PURAM, NEW DELHI-110 006, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 LALIT KUMAR MICROWAVE TUBE R & D CENTRE, BE COMPLEX, JALAHALLI P.O., BANGALORE-560013, INDIA.
2 KADOOR SEETHARAMA BHAT MICROWAVE TUBE R & D CENTRE, BE COMPLEX, JALAHALLI P.O., BANGALORE-560013, INDIA.
3 MEDURI RAVI MICROWAVE TUBE R & D CENTRE, BE COMPLEX, JALAHALLI P.O., BANGALORE-560013, INDIA.
4 PERUMAL DURGA DEVI MICROWAVE TUBE R & D CENTRE, BE COMPLEX, JALAHALLI P.O., BANGALORE-560013, INDIA.
5 KEDIGE SANTHOSH KUMAR MICROWAVE TUBE R & D CENTRE, BE COMPLEX, JALAHALLI P.O., BANGALORE-560013, INDIA.
PCT International Classification Number H01J 1/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA