US3273005A - Electron emitter utilizing nitride emissive material - Google Patents
Electron emitter utilizing nitride emissive material Download PDFInfo
- Publication number
- US3273005A US3273005A US269352A US26935263A US3273005A US 3273005 A US3273005 A US 3273005A US 269352 A US269352 A US 269352A US 26935263 A US26935263 A US 26935263A US 3273005 A US3273005 A US 3273005A
- Authority
- US
- United States
- Prior art keywords
- nitride
- emitter
- cathode
- electron
- thermionic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/14—Solid thermionic cathodes characterised by the material
- H01J1/148—Solid thermionic cathodes characterised by the material with compounds having metallic conductive properties, e.g. lanthanum boride, as an emissive material
Definitions
- an object of this invention to provide an electron emitter which is relatively simple to manufacture and does not require special processing for rendering it an effective emitter of electrons.
- the nit-rides of the rare earth metals of the lanthanide series are thermionically emissive and form the essential ingredient of emitters having superior properties.
- These compounds are of the type MeN where Me is the symbol for the metal and N is the symbol for nitrogen. They crystallize in a compact structure yielding high melting points, low evaporation rate and extreme hardness.
- the compounds can be relatively easily formed during manufacture by heating a cathode constituted in part of the selected metal, such as cerium, for example, to a temperature in the order of 1340 C., in the presence of ammonia gas.
- FIGURE 1 illustrates the emission characteristics of a number of emitters embodying the present invention
- FIGURE 2 illustrates the relative evaporation rates of two emitters embodying the present invention
- FIGURE 3 illustrates a cathode embodying the present invention
- FIGURE 4 shows a step in the manufacture of the cathode of FIGURE 3
- FIGURE 5 shows another step in the manufacture of the cathode of FIGURE 3;
- FIGURE 6 shows a cross-sectional view of another cathode embodying the present invention.
- FIGURE 7 shows a cross-sectional view of yet another cathode embodying the present invention.
- nitrides of the rare earth metals of the lanthanide series having atomic numbers 57 through 71
- thorium and uranium are thermionically electron emissive in such significant degree as to render these materials highly desirable for use as electron emitters.
- These materials also possess the requisite physical characteristics of thermionic emitters and are relatively easy to manufacture. The latter is, of course, considerable commercial importance.
- the highly desirable physical characteristics of the nitrides of the lanthanide series, thorium and uranium include: high melting points, extreme hardness, metallic conductivity and low evaporation at incandescent temperatures. These compounds are of the type MeN and crystallize in the face-centered cubic, or NaCl structure. These compounds are true interstitial compounds with nitrogen atoms occupying the octahedral holes in the interstices of the metal structure. This tightly bonded crystal structure undoubtedly contributes to the high order of thermal stability observed with these compounds.
- FIGURE 1 of the drawing A comparison of a number of nitrides of the present invention with some well-known emitters is shown in FIGURE 1 of the drawing in which emission current in amperes per cm. is plotted as a function of surface temperature in degrees Centigrade (as determined by an optical pyrometcr).
- a semi-logarithmic plot is chosen for the purpose of the illustration since the resulting curves are significant with respect to Dushmans equation of emission.
- Dushmans equation is stated in detail in many texts on thermionic emission, but for purposes of explaining the present invention, the equation may be more concisely stated as:
- A a semi-empirical constant; its units are amps. per cm? per degree Kelvin.
- T temperature of cathode in degrees Kelvin.
- e tl116 base of the natural or Naperian logarithms (approximately 2.72).
- FIGURE 2 of the drawing A comparison of the evaporation rate of the highly efficient thermionic emitters of the rare earth nitrides, cerium nitride and lanthanum nitride, with some well-known emitters is shown in FIGURE 2 of the drawing.
- evaporation rate of metal in grams per cm. per second is plotted as a function of electron emission in amperes per cm.
- An electron emitter normally is useful only if its evaporation rate is low. From the graph of FIGURE 2 it may be seen that lanthanum nitride and cerium nitride possess evaporation rates less than that of tungsten at equal rates of electron emission. The evaporation rates are only slightly greater than that of lanthanum hexaboride, which is known to possess an extremely low evaporation rate. Cerium nitride, for example, may be seen to possess particularly desirable properties for use as a thermionic emissive material in a cathode. Its efficiency as a thermionic emitter is higher than most known materials and its evaporation rate is low.
- FIGURE 3 A cathode embodying the present invention is shown in FIGURE 3.
- the cathode is of the hairpin variety and includes side support members and 11 which are connected to and carried by an assembly in the electron discharge device which is variously known as a stern, header or base.
- the emitter of the cathode is generally formed as an inverted V having opposite extremities secured, as by welding at and 16, to members 10 and 11, respectively.
- the emitter takes the form of a relatively large wire 12 having a smaller Wire 13 disposed thereabout in a plurality of turns 14. Extremities of wire 13 may be secured to wire 12, as by welding thereto, but, preferably, opposite extremities of wire 13 are secured to members 10 and 11 when the above-mentioned welds at 15 and 16 are consumated.
- the heater circuit for the emitter includes members '10 and 11, which are selected of a conductive refractory material, such as tungsten or molybdenum, and the circuit connection to the emitter is normally supplied through one of members 10 and ll.
- the cathode of FIGURE 3 has the advantage of mechanical ruggedness at some sacrifice in available surface area. Where requirements are less severe, wire 13 may be omitted and wire 12 may take the form of a gauze or a tightly wound coil suspended between members 10 and 11.
- a cathode such as is shown in FIGURE 3 is constructed, preferably, by first winding a small diameter wire 17 of refractory metal, such as tungsten or molybdenum, about another wire 18 of refractory material which may, or may not, be of the same refractory material as wire 17.
- refractory metal such as tungsten or molybdenum
- Wire 18 is then bent in the general form of a hairpin and secured at 15 and 16 to members 10 and 11, as shown in FIGURE 3. Extremities of wire 17 are also secured to members 10 and 11 at the same time.
- a coating 19, as seen in FIGURE 5, of the lanthanide series metals, thorium or uranium is then deposited on wire 18, and Wire 17 which is coiled thereabout.
- Such a coating can be effected by vapor-plating or dipping in molten metal, for example.
- the desired nitride may be formed by heating the cathode support to a temperature between 1200 C. and 1400 C. in the presence of ammonia, which is caused to flow into the electron discharge device.
- a support temperature of 1340 C. is particularly satisfactory, although, as with most similar chemical reactions, temperature and time provide inverse effects upon the extent of reaction and wide variations in both are possible.
- Resulting pyrolysis of the ammonia releases hydrogen which prevents the metal from oxidizing and the nascent nitrogen liberated rapidly reacts with the metal to provide the desired nitride coating.
- the electron discharge device is then out-gassed and processed in the normal manner. I have found that no activation schedule is required for these cathodes.
- a cathode embodying this invention and suitable for use in cathode ray tubes is shown in cross section in FIG- UR E 6.
- the cathode includes an arcuate base member 20 carrying a mesh 21 of refractory material having thermionic emissive nitride coating 22 thereabout.
- Coating 22 is indirectly heated by coil 23 which is formed of a resistive refractory material, such as tungsten.
- Lead 24 is connected to coating 22 and supplies the electrical circuit connection to the cathode emitter.
- base member 20 and mesh 21 may be constituted of insulating refractory materials, such as ceramic, although, in a preferred embodiment mesh 21 is constituted of molybdenum.
- the nitride coating 22 can be provided as described in connection with the cathode of FIGURE 3.
- FIGURE 7 A cross-sectional view of a cathode suitable for use in a planar electrode tube is presented in FIGURE 7.
- the cathode includes a support sleeve 26 which carries a base 27.
- a mesh 28, of refractory material, is secured to base 27 and provides mechanical support for nitride coating 29. Indirect heating is effected by coil 30.
- Sleeve 26 is constituted of a conductive refractory material, for example, tungsten or molybdenum, and provides electrical circuit connection to coating 29.
- the nitride emitters of the present invention may be used in any of a number of ways to provide the essential component of commercial cathodes. These cathodes possess the many desirable qualities resulting from the properties of the nitrides as described hereinbefore.
- the nitrides of this invention do not react with the usual refractory materials at incandescent temperatures and they are good conductors of electricity. Thus, a wide choice of suitable base materials and circuit connections are permitted.
- the metallic conductivity yields improved performance at high levels of emission.
- a thermionic cathode including an emitter consisting essentially of at least one metal nitride selected from the group consisting of the nitrides of thorium, uranium, and the lanthanide series rare earth metals, and means supporting said emitter providing a conductive connection therewith.
- a thermionic cathode including an emitter consisting essentially of at least one lanthanide series rare earth metal nitride and means supporting said emitter and providing a conductive connection therewith.
- a thermionic cathode including an emitter comprising as the essential ingredient thorium nitride and means supporting said emitter and providing a conductive connection therewith.
Landscapes
- Solid Thermionic Cathode (AREA)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US269352A US3273005A (en) | 1963-04-01 | 1963-04-01 | Electron emitter utilizing nitride emissive material |
FR969306A FR1387658A (fr) | 1963-04-01 | 1964-04-01 | Perfectionnements apportés aux cathodes et procédé de fabrication de ces cathodes |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US269352A US3273005A (en) | 1963-04-01 | 1963-04-01 | Electron emitter utilizing nitride emissive material |
Publications (1)
Publication Number | Publication Date |
---|---|
US3273005A true US3273005A (en) | 1966-09-13 |
Family
ID=23026891
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US269352A Expired - Lifetime US3273005A (en) | 1963-04-01 | 1963-04-01 | Electron emitter utilizing nitride emissive material |
Country Status (2)
Country | Link |
---|---|
US (1) | US3273005A (fr) |
FR (1) | FR1387658A (fr) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3440475A (en) * | 1967-04-11 | 1969-04-22 | Lokomotivbau Elektrotech | Lanthanum hexaboride cathode system for an electron beam generator |
US3531678A (en) * | 1968-06-24 | 1970-09-29 | Raytheon Co | Heater with boron nitride coating |
EP0732720A1 (fr) * | 1995-03-14 | 1996-09-18 | Hitachi, Ltd. | Cathode dispositif émetteur d'un faisceau d'électrons l'utilisant et procédé de fabrication de la cathode |
EP1983547A1 (fr) * | 2007-04-20 | 2008-10-22 | PANalytical B.V. | Source de rayons X |
US20100314540A1 (en) * | 2009-06-14 | 2010-12-16 | Adler David L | Electron microscope with an emitter operating in medium vacuum |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1698850A (en) * | 1923-03-31 | 1929-01-15 | Westinghouse Lamp Co | Activation of refractory metal filaments |
US1716545A (en) * | 1929-06-11 | Geobqe m | ||
US1733813A (en) * | 1921-08-01 | 1929-10-29 | Westinghouse Lamp Co | Composite body and method of producing the same |
US1883840A (en) * | 1930-07-16 | 1932-10-18 | Gen Electric | Manufacturing oxide cathodes |
US1895437A (en) * | 1931-03-24 | 1933-01-31 | Rca Corp | Method of degassing cathodes of electron discharge tubes |
US1954596A (en) * | 1928-04-05 | 1934-04-10 | Loewe Bernhard | Material for high emission cathodes |
US2659685A (en) * | 1950-03-31 | 1953-11-17 | Gen Electric | Boride cathodes |
US2742585A (en) * | 1952-08-22 | 1956-04-17 | Gen Electric | Electrical vapor detector |
US3139541A (en) * | 1960-07-05 | 1964-06-30 | Monsanto Co | Generation of power using emissive materials |
-
1963
- 1963-04-01 US US269352A patent/US3273005A/en not_active Expired - Lifetime
-
1964
- 1964-04-01 FR FR969306A patent/FR1387658A/fr not_active Expired
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1716545A (en) * | 1929-06-11 | Geobqe m | ||
US1733813A (en) * | 1921-08-01 | 1929-10-29 | Westinghouse Lamp Co | Composite body and method of producing the same |
US1698850A (en) * | 1923-03-31 | 1929-01-15 | Westinghouse Lamp Co | Activation of refractory metal filaments |
US1954596A (en) * | 1928-04-05 | 1934-04-10 | Loewe Bernhard | Material for high emission cathodes |
US1883840A (en) * | 1930-07-16 | 1932-10-18 | Gen Electric | Manufacturing oxide cathodes |
US1895437A (en) * | 1931-03-24 | 1933-01-31 | Rca Corp | Method of degassing cathodes of electron discharge tubes |
US2659685A (en) * | 1950-03-31 | 1953-11-17 | Gen Electric | Boride cathodes |
US2742585A (en) * | 1952-08-22 | 1956-04-17 | Gen Electric | Electrical vapor detector |
US3139541A (en) * | 1960-07-05 | 1964-06-30 | Monsanto Co | Generation of power using emissive materials |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3440475A (en) * | 1967-04-11 | 1969-04-22 | Lokomotivbau Elektrotech | Lanthanum hexaboride cathode system for an electron beam generator |
US3531678A (en) * | 1968-06-24 | 1970-09-29 | Raytheon Co | Heater with boron nitride coating |
EP0732720A1 (fr) * | 1995-03-14 | 1996-09-18 | Hitachi, Ltd. | Cathode dispositif émetteur d'un faisceau d'électrons l'utilisant et procédé de fabrication de la cathode |
US5763880A (en) * | 1995-03-14 | 1998-06-09 | Hitachi, Ltd. | Cathode, electron beam emission apparatus using the same, and method of manufacturing the cathode |
EP1983547A1 (fr) * | 2007-04-20 | 2008-10-22 | PANalytical B.V. | Source de rayons X |
WO2008129006A1 (fr) * | 2007-04-20 | 2008-10-30 | Panalytical B.V. | Source de rayons x |
US20100150315A1 (en) * | 2007-04-20 | 2010-06-17 | Bart Filmer | X-ray source |
US8223923B2 (en) | 2007-04-20 | 2012-07-17 | Panaltyical B.V. | X-ray source with metal wire cathode |
US20100314540A1 (en) * | 2009-06-14 | 2010-12-16 | Adler David L | Electron microscope with an emitter operating in medium vacuum |
US8729470B2 (en) * | 2009-06-14 | 2014-05-20 | DLA Instruments | Electron microscope with an emitter operating in medium vacuum |
Also Published As
Publication number | Publication date |
---|---|
FR1387658A (fr) | 1965-01-29 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3312856A (en) | Rhenium supported metallic boride cathode emitters | |
US2107945A (en) | Cathode structure | |
US5170422A (en) | Electron emitter for an x-ray tube | |
US3558966A (en) | Directly heated dispenser cathode | |
US3928783A (en) | Thermionic cathode heated by electron bombardment | |
CN108878232B (zh) | 用于真空电子器件的热阴极组件 | |
US2741717A (en) | Dispenser type cathode having gettercoated parts | |
US3134924A (en) | Emissive materials of a metal matrix with molecularly dispersed additives | |
US3273005A (en) | Electron emitter utilizing nitride emissive material | |
US2201731A (en) | Discharge tube electrode assembly | |
US2438732A (en) | Electron tube cathode | |
US2497111A (en) | Electron tube having carburized thoriated cathode | |
US2246131A (en) | Electron emitting body | |
US2212827A (en) | Hot cathode for high power | |
US1874753A (en) | Controlled arc discharge apparatus | |
US3553521A (en) | Indirectly heated cathode for an electron discharge tube with an insulated heating element | |
US2879429A (en) | High power electron tube | |
US3495120A (en) | Microheating elements,more particularly for cathodes of electron tubes | |
US4265666A (en) | Boron carbide La, Sr and/or Ba hexaboride ceramic material for a low temperature direct heating electric gun cathode | |
US3093757A (en) | Device for converting thermal energy into electrical energy | |
US2172968A (en) | Electric discharge tube | |
US2072576A (en) | Nickel base alloy | |
US2106855A (en) | Space-current device | |
US2879432A (en) | Electron emitter | |
US2273762A (en) | Incandescible cathode |