Calcium-containing barium scandium aluminate for impregnated diffusion cathode and preparation method thereof

A barium scandium aluminate, diffusion cathode technology, applied in chemical instruments and methods, parts of discharge tubes/lamps, inorganic chemistry, etc., can solve the problems of narrow temperature range, low diffusion rate, uneven emission, etc. Consistent phase structure, lower immersion temperature, and simple preparation process

Active Publication Date: 2020-06-12
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Through research, it is found that the phase structure of aluminates doped with scandium oxide mainly includes Ba 3 CaAl 2 o 7 、Ba 5 CaAl 4 o 12 、Sc 2 o 3 and other compounds, but in aluminate Sc or Sc 2 o 3 The diffusion rate is very low, resulting in Sc or Sc on the emitting surface when the cathode is working 2 o 3 The problem of insufficient supply and uneven distribution will eventually lead to low emission current density and uneven emission of the cathode
Secondly, the phase structure contained in traditional aluminates and scandium-containing aluminates can exist in a very narrow temperature range (about 1000-1200°C), and the high impregnation temperature makes it impossible to guarantee the consistency of the phase structure before and after the impregnation process
Moreover, the existing synthetic methods are also difficult to repeatedly obtain scandium-containing aluminates with consistent phase composition.

Method used

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  • Calcium-containing barium scandium aluminate for impregnated diffusion cathode and preparation method thereof
  • Calcium-containing barium scandium aluminate for impregnated diffusion cathode and preparation method thereof
  • Calcium-containing barium scandium aluminate for impregnated diffusion cathode and preparation method thereof

Examples

Experimental program
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Effect test

Embodiment 1

[0031] What this example prepares is Ba 1.8 Ca 0.2 ScAlO 5 Powder, prepared as follows:

[0032] According to Ba 2+ , Ca 2+ 、Sc 3+ 、Al 3+ The molar ratio of cations is 1.8:0.2:1:1 ratio to calculate 0.018mol of Ba(NO 3 ) 2 , 0.002mol of Ca(NO 3 ) 2 4H 2 O, 0.01mol of Sc(NO 3 ) 3 ·6H 2 O and 0.01mol of Al(NO 3 ) 3 9H 2O mass and accurately weighed. Put all the raw materials into a beaker, add 400 mL of deionized water to obtain a mixed solution with a total molar concentration of metal cations of 0.1 mol / L. The total number of moles of all metal cations in the mixed solution is 0.04mol. In order to completely precipitate the cations, the moles of the ammonium carbonate precipitation agent are weighed to be twice the sum of the moles of all cations, which is 0.08mol. After accurate weighing, it is configured into a 2.0mol / L sodium carbonate solution. Use a magnetic heating stirrer to make the mixed solution of the raw materials fully uniform, then pour the amm...

Embodiment 2

[0035] In order to study Ba 1.8 Ca 0.2 ScAlO 5 The temperature range where the phase structure can exist stably, because Ba 1.8 Ca 0.2 ScAlO 5 with Ba 2 ScAlO 5 The crystal structure of is similar, this embodiment has prepared the Ba of different temperature sintering 2 ScAlO 5 powder. The difference between this embodiment and embodiment 1 is that according to Ba 2+ 、Sc 3+ 、Al 3+ The molar ratio of cations is 2:1:1, and 0.02mol of Ba(NO 3 ) 2 , 0.01mol of Sc(NO 3 ) 3 ·6H 2 O and 0.01mol of Al(NO 3 ) 3 9H 2 The mass of O was accurately weighed and Ca was not added 2+ , the sintering temperature was adjusted to 1000°C, 1200°C, 1400°C and 1600°C respectively, and the other steps remained unchanged. The purpose is to prepare Ba at different sintering temperatures 2 ScAlO 5 , verify that the Ba produced by the present invention 2 ScAlO 5 It has a wide temperature range in which the phase structure can exist stably.

[0036] image 3 It is the Ba of differ...

Embodiment 3

[0038] What this example prepares is Ba 1.5 Ca 0.5 ScAlO 5 Powder, the difference between this embodiment and embodiment 1 is that according to Ba 2+ , Ca 2+ 、Sc 3+ 、Al 3+ The molar ratio of cations is 1.5:0.5:1:1, and 0.015mol of Ba(NO 3 ) 2 , 0.005mol of Ca(NO 3 ) 2 4H 2 O, 0.01mol of Sc(NO 3 ) 3 ·6H 2 O and 0.01mol of Al(NO 3 ) 3 9H 2 The quality of O, and accurately weighed, other steps remain unchanged. The purpose is to adjust the ratio of each component to verify the importance of the raw material composition of the present invention.

[0039] Figure 4 Be that embodiment 3 makes Ba 1.5 Ca 0.5 ScAlO 5 Powder X-ray diffraction results, X-ray diffraction patterns and Ba 2 ScAlO 5 (β phase, PDF card number is 43-0078) The diffraction spectrum is consistent, indicating that the single-phase Ba was successfully prepared 2 ScAlO 5 .

[0040] The Ba that embodiment 3 obtains 1.5 Ca 0.5 ScAlO 5 The powder was used as an impregnating substance to prep...

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Abstract

The invention discloses calcium-containing barium scandium aluminate for dipping a diffusion cathode and a preparation method thereof, and belongs to the field of manufacturing of vacuum electronic devices. The structural formula of the calcium-containing barium scandium aluminate is Ba<2-x>Ca<x>Sc<Al>O<5>, wherein x is greater than or equal to 0.1 and less than or equal to 0.5. The preparation method is a liquid-phase coprecipitation method and comprises the following steps: dissolving water-soluble barium salt, calcium salt, scandium salt and aluminum salt in deionized water, mixing and stirring the solution with an ammonium carbonate solution, filtering and cleaning the solution to obtain a precursor, tabletting the precursor, and sintering the precursor in a muffle furnace at 1000-1600DEG C for 4-5 hours to obtain calcium-containing barium scandium aluminate. The prepared calcium-containing barium scandium aluminate has a single Ba2ScAlO5 close-packed hexagonal crystal structure,a cathode impregnated with the active substance can provide direct-current emission current density close to 11.51 A / cm2 at 1000 DEG C, and the low-temperature high-current density characteristic of an impregnated diffusion cathode is achieved. The preparation method of the calcium-containing barium scandium aluminate is good in repeatability, high in yield, simple in preparation process and suitable for industrial popularization.

Description

technical field [0001] The invention belongs to the field of manufacturing vacuum electronic devices, and in particular relates to calcium-containing barium scandium aluminate for impregnating and diffusing cathodes and a preparation method thereof. Background technique [0002] Vacuum electronic devices are widely used in broadcast communication, radar, navigation, electronic countermeasures and medical diagnosis and treatment. The cathode is the source of electron emission in vacuum electronic devices, known as the "heart" of vacuum electronic devices. At present, the most widely used in vacuum electronic devices is the impregnated diffusion cathode, which is made by impregnating the molten active material into the porous tungsten matrix. This type of cathode has been widely used in medium and low power microwave vacuum electronic devices. applications, but it cannot meet the requirements of millimeter-wave devices and high-power microwave devices with high emission curre...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/50C04B35/622C01F17/32H01J1/142
CPCC04B35/50C04B35/622H01J1/142C04B2235/3208C04B2235/3215C04B2235/3217C04B2235/602C04B2235/656C04B2235/6567C04B2235/6562C01P2002/72C01P2006/40
Inventor 付浩郑强黄政虎伍风翼刘蔓鄢然罗勇
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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