The metallurgical properties of tungsten–iridium cathodes

Vancil, Bernard; Mueller, Robert A.; Steele, Edward R; Ohlinger, Wayne L.; Wintucky, Edwin G.

doi:10.1016/s0169-4332(99)00063-x

Cited by 5 publications

(4 citation statements)

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“…Li et al found that 5 W biased films were quite stable, but the reason for this stability could be due to a combination of aspects such as texture and thickness, or film density. 11 Much of the available literature on work function cites values that were obtained indirectly, using cathode emission test data. Directly measuring the work function of a dispenser cathode would provide valuable insight into the nature of the activated surface without the numerous sources of error associated with calculating the effective work function from CSD tests.…”

Section: Resultsmentioning

confidence: 99%

“…[6][7][8][9] Additionally, the microstructure of the substrate material, W or a mixed-metal matrix, has been investigated. [10][11][12] However, few studies have investigated the microstructure of the coating itself and how it relates to cathode performance. Liu et al investigated a nanoparticle thin film coating of Ir and its effect on thermionic emission.…”

Section: Introductionmentioning

confidence: 99%

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Correlation between microstructure and thermionic electron emission from Os-Ru thin films on dispenser cathodes

Swartzentruber

Balk

Effgen³

2014

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Right click to open a feedback form in a new tab to let us know how this document benefits you.Osmium-ruthenium films with different microstructures were deposited onto dispenser cathodes and subjected to 1000 h of close-spaced diode testing. Tailored microstructures were achieved by applying substrate biasing during deposition, and these were evaluated with scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy before and after close-spaced diode testing. Knee temperatures determined from the close-spaced diode test data were used to evaluate cathode performance. Cathodes with a large {10-11} Os-Ru film texture possessed comparatively low knee temperatures. Furthermore, a low knee temperature correlated with a low effective work function as calculated from the close-spaced diode data. It is proposed that the formation of strong {10-11} texture is responsible for the superior performance of the cathode with a multilayered Os-Ru coating.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Correlation between microstructure and thermionic electron emission from Os-Ru thin films on dispenser cathodes

Swartzentruber

Balk

Effgen³

2014

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…In order to reduce the work function of the dispenser cathode surface, the emissive materials, which are barium-calcium aluminates, are diffused into tungsten pellet pores [1]- [6]. The specific molar ratio of barium oxide, calcium oxide, and aluminum oxide (BaO:CaO:Al 2 O 3 ) is 5:3:2.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Nanocrystalline Electron Emissive Materials with Homogenous Composition in Nanoscale

Shiran¹,

Hadianfard²,

Shiezadeh³

2013

IJCEA

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Abstract-In this research, specific stoichiometric mixture of nanocrystalline barium carbonate, calcium carbonate, and aluminum oxide was fabricated by using the sol-gel combustion method. This mixture is used as emissive materials on impregnated cathodes which make up high power vacuum microwave tubes such as klystrons. Composition uniformity and particle size of emissive materials affect the electron emission properties of impregnated cathodes. In this study, dry gel and heat treated powder at 500 °C are investigated by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results show that dry gel combusts at 260 °C , and that during combustion transforms from an amorphous phase to a nanocrystalline phase. The average crystallite size of the powders which is calculated by Debye-Scherrer's method based on the XRD patterns is under 45 nm. The results of SEM and EDX of powder after heat treatment at 500 °C show that the particle size of powder is under 100 nm, and the chemical composition of emissive material is uniform at nanoscale.Index Terms-Dispenser cathode, emissive material, nanopowder, sol-gel combustion synthesis.

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“…Thermionic dispenser cathodes are widely used in fabricating electron beam devices due to the production of high current density at low temperatures. In order to reduce the work function of the dispenser cathode surface, the emissive materials, barium-calcium aluminates, are diffused into tungsten pellet pores [1][2][3][4][5][6]. The surface of M type cathode, a kind of dispenser cathodes, is coated either by a thin layer of refractory metals such as osmium, iridium, ruthenium, or a layer of osmium-iridium or osmium-ruthenium.…”

Section: Introductionmentioning

confidence: 99%

Study the Effect of Nanoemissive Materials on M-Type Cathode Performance

Chaharsoughi

Hadianfard

Shiezadeh

2013

AMR

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In this study, the stoichiometric mixture of barium carbonate, calcium carbonate, and aluminum oxide with ratio of 5:3:2 was produced by two individual methods: sol-gel combustion and ball-milling method used as a precursor of electron emissive material on impregnated cathodes which make up high power vacuum microwave tubes such as klystrons. Results from X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy on emissive material produced by sol-gel combustion technique show that its crystallite size is under 45 nm, and particle size is less than 100 nm, and the chemical composition of emissive material is uniform at nanoscale. The effects of two types of emissive materials on operation properties of M type cathode were also investigated. The two types of manufactured M cathodes were tested inside an electron gun under maximum anode voltage 10.5 kV in continues wave mode, at 1100 ͦC, and the anode-cathode distance was fixed at 5 mm. results show that the emission current of M cathode impregnated by nano emissive materials is more uniform than conventional cathode, and its current density is about 2.7 A/cm2, while in I-V curve it does not reach at saturated-emission region at 10.5 kV.

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The metallurgical properties of tungsten–iridium cathodes

Cited by 5 publications

References 1 publication

Correlation between microstructure and thermionic electron emission from Os-Ru thin films on dispenser cathodes

Correlation between microstructure and thermionic electron emission from Os-Ru thin films on dispenser cathodes

Synthesis of Nanocrystalline Electron Emissive Materials with Homogenous Composition in Nanoscale

Study the Effect of Nanoemissive Materials on M-Type Cathode Performance

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