Scandate Dispenser Cathodes With Sharp Transition and Their Application in Microwave Tubes

Vancil, Bernard; Brodie, I.; Lorr, John; Schmidt, Victor

doi:10.1109/ted.2014.2309279

Cited by 39 publications

(21 citation statements)

References 12 publications

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“…The performances of the SD and SG are similar to that of the top-layer cathode prepared by Gärtner et al [14]. But Vancil et al [10,41] and Yamamoto et al [42] found that the cathode prepared with the powder by LS method also could provide a highemission property.…”

Section: Development Of the Scandia-doped Tungsten Matrix Impregnatedsupporting

confidence: 60%

“…A large number of studies showed that based on the current widely used Ba-W cathode, the addition of a certain amount of scandia can significantly improve the emission performance. Therefore, the scandate cathode is considered as one of the main candidates for the next generation high current density cathodes [4][5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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A review on scandia doped tungsten matrix scandate cathode

et al. 2019

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As the cathode with the highest electron emission capability in the thermionic cathode, the scandate cathode has attracted more and more attention in recent years, especially the scandia doped tungsten matrix scandate cathode. Experimental studies show that scandia doped tungsten matrix scandate cathodes with submicron microstructures exhibit excellent emission capacity, and the pulse emission current density in the space-charge region can be over 35 A cm −2 at 850 °C b. In the direct current (DC) condition with temperature compensation, the emission current density could reach 25 A cm −2 at 850 °C b. The device lifetime is over 3700 h after operating at 950 °C b with the DC loading of 40 A cm −2. The emission mechanism of the scandate cathode including the effect of the surface structure and composition on the work function of the cathode are systematically reviewed.

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Section: Development Of the Scandia-doped Tungsten Matrix Impregnatedsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

A review on scandia doped tungsten matrix scandate cathode

et al. 2019

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“…Then researchers paid a lot of effort to increase the electron emission capability by controlling the introducing approaches of Sc and the microstructure of the obtained cathodes, and advanced strategies including the liquid-liquid (L-L) precipitation method, liquid-solid (L-S) precipitation method [73] and pulse laser deposition (PLD) technology [74] are developed to improve the distribution uniformity of the scandium oxide. Up to now, Sc-cathodes have been considered as one of the most potential candidates for the next generation cathodes with high current density [75][76][77], and could be divided into three different types [45]: the top-layer scandate cathode [72], impregnated scandate cathode (Sc 2 O 3 was mixed with Ba-Ca-aluminate impregnant) and scandia-doped dispenser (SDD) cathode [78].…”

Section: Sc-cathodementioning

confidence: 99%

A review on recent progress of thermionic cathode

et al. 2020

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As the performance of vacuum electron devices is essentially governed by the properties of their cathodes, developing efficient and durable thermionic cathode is necessary and highly desired to meet the boosting requirements of vacuum electron devices. This review summarized the progress made in the past decades with a detailed discussion on the occurred various thermionic cathodes and their features, and the understandings of the correlation between the emission properties and the composition, where structure and synthesis method are well illustrated. Furthermore, dispenser cathodes with novel structures and emission mechanism are highlighted to indicate the recent achievement in this area of research, and Sc-cathode is considered as a promising candidate for the next-generation vacuum electron devices due to the greatly improved efficiency. However, challenges still exist to meet the ever-growing demands of thermionic cathode with collaborative requirement of high performance, easy fabrication and inadequate reproducibility.

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“…Figure 2 contains surface structures of the most stable simulated structures under thermionic cathode operating conditions for the (001) (Figure 2A), (011) (Figure 2B), (111) (Figure 2C), (210) (Figure 2D), (211) (Figure 2E Figure 3D. 59 synthesis. The length scale of these partially sintered crystals is about 100-500 nm.…”

Section: Mainmentioning

confidence: 99%

Work function and surface stability of tungsten-based thermionic electron emission cathodes

2017

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Materials that exhibit a low work function and therefore easily emit electrons into vacuum form the basis of electronic devices used in applications ranging from satellite communications to thermionic energy conversion. W-Ba-O is the canonical materials system that functions as the thermionic electron emitter used commercially in a range of high power electron devices. However, the work functions, surface stability, and kinetic characteristics of a polycrystalline W emitter surface are still not well understood or characterized. In this study, we examined the work function and surface stability of the eight lowest index surfaces of the W-Ba-O system using Density Functional Theory methods. We found that under the typical thermionic cathode operating conditions of high temperature and low oxygen partial pressure, the most stable surface adsorbates are Ba-O species with compositions in the range of Ba 0.125 O to Ba 0.25 O per surface W atom, with O passivating all dangling W bonds and Ba creating work function-lowering surface dipoles. Wulff construction analysis reveals that the presence of O and Ba significantly alters the surface energetics and changes the proportions of surface facets present under equilibrium conditions. Analysis of previously published data on W sintering kinetics suggests that fine W particles in the size range of 100-500 nm may be at or near equilibrium during cathode synthesis, and thus may exhibit surface orientation fractions well-described by the calculated Wulff construction.

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Scandate Dispenser Cathodes With Sharp Transition and Their Application in Microwave Tubes

Cited by 39 publications

References 12 publications

A review on scandia doped tungsten matrix scandate cathode

A review on scandia doped tungsten matrix scandate cathode

A review on recent progress of thermionic cathode

Work function and surface stability of tungsten-based thermionic electron emission cathodes

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