Thermionic cathode surfaces: the state-of-the-art and outstanding problems

Tuck, R.A.

doi:10.1016/0042-207x(83)90597-3

Cited by 38 publications

(12 citation statements)

References 21 publications

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“…It can be seen from the I collect − V driven curve that, I collect becomes measurable when the V driven is larger than ≈3.1 V. It then increases exponentially with V driven and approaches ≈20 µA at V driven = 3.9 V. Taking the horizontally projected area of emitting SACNT films (S = 1500 µm 2 ) into consideration, an emission current density up to ≈1.33 A cm −2 is obtained, which is comparable to that of commercial thermionic electron emitters. [19,20] The driven voltage as a function of emission current density from the device measured in Figure 2b together with those of previously reported gated FEAs [21][22][23][24][25][26] are plotted on the same graph in Figure 2c. Here, driven voltage of FEAs refers to the voltage applied to the gate electrode.…”

Section: Thermionic Electron Emission Characteristics Of Single Micromentioning

confidence: 91%

High‐Performance On‐Chip Thermionic Electron Micro‐Emitter Arrays Based on Super‐Aligned Carbon Nanotube Films

Wang

Yang

et al. 2019

Adv Funct Materials

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An important advancement towards the realization of miniaturized and fully integrated vacuum electronic devices will be the development of on‐chip integrated electron sources with stable and reproducible performances. Here, the fabrication of high‐performance on‐chip thermionic electron micro‐emitter arrays is demonstrated by exploiting suspended super‐aligned carbon nanotube films as thermionic filaments. For single micro‐emitter, an electron emission current up to ≈20 µA and density as high as ≈1.33 A cm−2 are obtained at a low‐driven voltage of 3.9 V. The turn‐on/off time of a single micro‐emitter is measured to be less than 1 µs. Particularly, stable (±1.2% emission current fluctuation for 30 min) and reproducible (±0.2% driven voltage variation over 27 cycles) electron emission have been experimentally observed under a low vacuum of ≈5 × 10−4 Pa. Even under a rough vacuum of ≈10−1 Pa, an impressive reproducibility (±2% driven voltage variation over 20 cycles) is obtained. Moreover, emission performances of micro‐emitter arrays are found to exhibit good uniformity. The outstanding stability, reproducibility, and uniformity of the thermionic electron micro‐emitter arrays imply their promising applications as on‐chip integrated electron sources.

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Section: Thermionic Electron Emission Characteristics Of Single Micromentioning

confidence: 91%

High‐Performance On‐Chip Thermionic Electron Micro‐Emitter Arrays Based on Super‐Aligned Carbon Nanotube Films

Wang

Yang

et al. 2019

Adv Funct Materials

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“…Pure metals of W, Ta and Re could be used as cathodes, because they can produce thermionic current lower than 1 A•cm -2 in operating temperature of above 1727 °C [10]. Among these metals, W attracted noticeable attention in industrial applications due to its high thermal resistance and could deliver a current density of 1.5 × 10 -7 A•cm -2 with work function of 4.54 eV at 1227 °C [11]. Thus, W-based thermionic cathodes are widely applied in large power concussion machine and electron beam instrument and exhibits the advantages of stable emission and good resistance to ion beam bombardment [12].…”

Section: Pure Metal Cathodesmentioning

confidence: 99%

“…Thus, W-based thermionic cathodes are widely applied in large power concussion machine and electron beam instrument and exhibits the advantages of stable emission and good resistance to ion beam bombardment [12]. However, the ultra-high operating suffers the decreased service life of the heating assembly devices [11], and enhancing the emission ability at low temperature is critical to further widen its applications.…”

Section: Pure Metal Cathodesmentioning

confidence: 99%

“…Up to now, oxide cathodes are widely used in receiving tube and TWT [30] due to the easy preparation process, lower operating temperature, longer servicing life and higher electron emission than those of pure metal cathodes [31]. However, challenges still need to be overcome for the oxide cathodes, such as poisoning sensitivity, ohmic heating in the oxide layer [11], and unstable impurities of SiO 2 and MgO, which limit the further applications of the oxide cathodes.…”

Section: Oxide Cathodesmentioning

confidence: 99%

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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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“…Thermionic cathodes are widely used in vacuum and discharge devices that require high current density, such as x-ray tubes and fluorescent lamps [7,8]. Typically, thermionic cathodes are coated with low work function emission materials (usually barium-rich oxides), and operate at temperatures above 1000 0 C to enhance thermionic electron emission.…”

Section: Introductionmentioning

confidence: 99%

A New Carbon Nanotube-Based Field Enhanced Thermionic Cathode

Jin

Day

2004

MRS Proc.

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The electron emission properties and field enhancement effects of carbon nanotubes (CNTs) have been extensively studied. However, all of these studies focus only on the field emission aspect of the materials and its application in cold cathode electron emitters. So far, we have not seen any studies in the literature that link CNTs with thermionic cathodes, which are an equally important cathode type because of their many applications. We present a study of field enhanced electron emissions from a new type of cathode: the CNT-based field enhanced thermionic cathode. This new cathode consists of a metal substrate with CNTs grown on top of its surface. The CNTs are coated with thermionic emission materials (BaO, SrO, and CaO). This unique cathode structure takes advantage of both the field enhancement effect from CNTs and the high electron emission capability of thermionic materials. The electron emission properties of this new cathode, particularly the field enhancement factor and effective work function, are compared with the conventional thermionic cathodes that are made of same oxide coating.

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Thermionic cathode surfaces: the state-of-the-art and outstanding problems

Cited by 38 publications

References 21 publications

High‐Performance On‐Chip Thermionic Electron Micro‐Emitter Arrays Based on Super‐Aligned Carbon Nanotube Films

High‐Performance On‐Chip Thermionic Electron Micro‐Emitter Arrays Based on Super‐Aligned Carbon Nanotube Films

A review on recent progress of thermionic cathode

A New Carbon Nanotube-Based Field Enhanced Thermionic Cathode

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