I.P. Li – Ph.D.(Eng.), Head of the Technical Center of Pluton JSC (Moscow)

E-mail: info@pluton.msk.ru

In microwave ovens (microwave ovens), primarily magnetrons, oxide-nickel thermionic electron cathodes (thermocathodes) are traditionally used as electron sources. A compound of alkaline earth metal oxides (BaSrCa)O, placed in the form of a coating on a nickel surface or in the bulk of a nickel matrix, is formed inside the magnetron by heat treatment of triple carbonate (BaSrCa)CO3, since these oxides are unstable in a normal atmosphere of air. The most stable emission properties during operation in magnetrons are possessed by pressed oxide-nickel cathodes formed by mixing, pressing and sintering of nickel and triple carbonate powders.

Existing technologies for the manufacture of initial powders in the production of pressed oxide-nickel thermal cathodes will no longer be able to provide the level of technical requirements for them in terms of quality, in particular the content of impurities, especially carbon.

In this paper, new technologies for the processing and synthesis of powders of carbonyl nickel and triple carbonate (TKA1-6) are proposed. The technique for producing high-purity nickel powder was washing carbonyl nickel in distilled water, drying and then annealing it in a hydrogen atmosphere, and the method of synthesis of powders (BaSrCa)CO3 consisted in processing solutions of Ba, Sr, Ca nitrates taken in predetermined proportions together with potassium orthophosphate at various temperatures.

To study the properties and composition of the obtained powders of highly pure materials, we used a MOMQ-1500D derivatograph, Bruker DRON-3M and D2PHACER diffractometers for X-ray phase analysis, a Riqaku high-temperature diffractometer for phase transition studies, a scanning electron microscope of the TESCAN VEGA fluorescence analysis type for X-ray fluorescence analysis.

Using the data of analytical devices and instruments, experimental research results are also presented in this work.

It turned out that in carbonyl nickel subjected to the above types of processing, the carbon content was more than 20 times lower than its content in the original powder. At the same time, the content of impurities in the synthesized ternary carbonate powder was observed in potentially smaller amounts compared to previously achieved for TKA1-6 from other manufacturers.

When testing various options for samples of pressed nickel oxide cathodes in the examined devices, the best results in the uniformity of emission properties along the surface of the thermal cathodes, as well as in durability were found in those made of especially pure powders, where triple carbonate was used as a coating on nickel agglomerates, mixed, pressed and sintered together with carbonyl nickel powder.

1. Kiselev A.B. Metallooksidnye katody elektronnyh priborov. M.: Izd-vo MFTI. 2001. 240 s. (In Russian).
2. Tomilin N.A., Seregin V.S., Marin V.P. i dr. Metodologiya i metody fiziko-himicheskogo analiza v razrabotke tekhnologicheskih processov proizvodstva elektronnoj komponentnoj bazy. Naukoemkie tekhnologii. 2016. T. 17. № 1. S. 37–47 (In Russian).
3. Ashkinazi L.A., Korzhavyj A.P. Termoelektronnye i vtorichno-elektronnye katody dlya EVP. Obzory po elektronnoj tekhnike. Ser. 6. Materialy. 1986. Vyp. 8 (1234). 58 s. (In Russian).
4. Kapustin V.I., Korzhavyj A.P. Fizika elektronnyh materialov dlya vakuumnyh mikrovolno-vyh priborov. Elektromagnitnye volny i elektronnye sistemy. 2016. T. 21. № 1. S. 42–52 (In Rus-sian).
5. Korzhavyj A.P., Kapustin V.I., Koz'min G.V. Metody eksperimental'noj fiziki v izbran-nyh tekhnologiyah zashchity prirody i cheloveka: Monografiya. M.: INFRA-M. 2016. 351 s. (In Russian).
6. Kapustin V.I. Fiziko-himicheskie osnovy sozdaniya mnogokomponentnyh oksidosoderzhashchih katodnyh materialov. Perspektivnye materialy. 2000. № 2. S. 5–17 (In Russian).
7. Lipeles R.A., Kan H.K.A. Chemical Stability of Barium Calcium Aluminate Dispenser Cathode Im-pregnants. Application of Surface Science. 1983. V. 16. P. 189–206.
8. Wittberg T.N., Wolf I.D., Harmes R.S. Somecomparative surface studies of two type of nickel matrix cathodes. Appl. Surf. Sci. 1981. V. 7. № 1/2. P. 156–157.
9. Polyakov S.V., Silaev A.D., Ledencova N.E. i dr. Puti sovershenstvovaniya konstrukcii i tekh-nologii izgotovleniya katodov dlya magnetronov korotkovolnovoj chasti millimetrovogo diapazo-na dlin voln. Naukoemkie tekhnologii. 2014. T. 15. № 11. S. 51–56 (In Russian).
10. Kapustin V.I., Marin V.P. Isparenie okislov pod dejstviem elektronnoj bombardirovki. Radiotekhnika i elektronika. 1983. T. 28. № 6. S. 1159–1162  (In Russian).
11. Dyubua B.Ch., Polivnikova O.V. O nekotoryh osobennostyah i problemah sovremennyh effek-tivnyh katodov. Elektronnaya tekhnika. Ser. 1. SVCHtekhnika. 2013. Vyp. 4(519). S. 187–190 (In Russian).
12. Korzhavyj A.P., Loginov B.M., Loginova M.B. i dr. Issledovanie metodami komp'yuternogo modelirovaniya nanoskopicheskih harakteristik kompozicionnyh materialov. Naukoemkie tekhno-logii. 2017. T. 18. № 2. S. 53–63 (In Russian).
13. Li I.P., Bondarenko G.G. Application of Hydrogen Vacuum Treatment of Palladium Powders for Production of Efficient Metal Alloy Cathodes of Self_Heated Magnetron. Inorganic Materials: Applied Research. 2012. V. 3. № 5. R. 381–384.
14. Ledencova N.E. Elektronnaya struktura i tekhnologii oksidno-nikelevyh katodnyh materia-lov: Dis. …kand. tekhn. nauk. M. 2019. 167 s. (In Russian).
15. Ledencova N.E., Li I.P. Issledovanie vozmozhnosti sozdaniya pressovannyh oksidno-nikelevyh katodov dlya magnetronov santimetrovogo diapazona dlin voln. Fundamental'nye pro-blemy radioelektronnogo priborostroeniya: Materialy Mezhdunarodnoj nauchno-tekhnicheskoj konferencii «Intermatic-2014». M.: MGTU MIREA. 2014. CH. 3. S. 156–158. (In Russian).
16. Li I.P. Magnetrony impul'snogo dejstviya – vse delo v katode. Elektronika. NTB. 2012. № 5. S. 84–87 (In Russian).
17. Patent RF № 2579006. Magnetron s pressovannym oksidno-nikelevym katodom. I.P. Li, F.V. Bazhanov, N.E. Ledencova i dr. Opubl. 27.03.2016. Byul. № 9 (In Russian).
18. Ledencova N.E., Li I.P. Aglomeraty nikelya i trojnogo karbonata (Ba, Ca, Sr) v proizvodstve pressovannyh oksidno-nikelevyh katodov dlya magnetronov santimetrovogo diapazona dlin voln. Materialy ezhegodnoj nauchno-tekhnicheskoj konferencii studentov, aspirantov i molodyh speci-alistov NIU VSHE im. E.V. Armenskogo. M.: MIEM NIU VSHE. 2015. S. 277–278 (In Russian).