Emission properties of top-layer scandate cathodes prepared by LAD

Gärtner, G.; Geittner, P.; Lydtin, H.; Ritz, A.

doi:10.1016/s0169-4332(96)00698-8

Cited by 136 publications

(81 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Similar values were obtained for a Therm-8 sample. These @ and A* values are considerably larger and smaller, respectively, than those found for top layer scandate cathodes (Gartner, 1997). Although these values are based on the full voltage drop across the diode, we find that space charge correction (Hasker, 1989) produces a minimal change indicating true limited emission fiom the cathode.…”

Section: Resultsmentioning

confidence: 52%

“…Saito et al have shown that depositing a capping layer of scandia (Sc,O,) improves the longevity of traditional BSCO emitters (Saito, 1990). The role of scandia has been recognized for some time in higher operating temperature tungsten based dispenser cathodes (Gartner, 1997). The primary problem with BSCO films is that deposition from carbonate precursors is required with a subsequent activation stage that releases CO,, trapped H,O and suboxides.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of sputter deposited thin film scandate cathodes for miniaturized thermionic converter applications

Zavadil¹,

Ruffner²,

King³

1999

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. We have successfully developed a method for fabricating scandate-based thermionic emitters in thin film form. The primary goal of our effort is to develop thin film emitters that exhibit low work function, high intrinsic electron emissivity, minimum thermal activation properties and that can be readily incorporated into a microgap converter. Our approach has been to incorporate BaSrO into a SGO, matrix using rf sputtering to produce thin films. Diode testing has shown the resulting films to be electron emissive at temperatures as low as 900 K with current densities of 0.1 mA.cm-2 at 1100 K and saturation voltages. We calculate an approximate maximum work function of 1.8 eV and an apparent emission constant (Richardson's constant, A*) of 36 mA.cm-z.K-2. Film compositional and structural analysis shows that a significant surface and subsurface alkaline earth hydroxide phase can form and probably explains the limited utilization and stability of Ba and its surface complexes. The flexibility inherent in sputter deposition suggests alternate strategies for eliminating undesirable phases and optimizing thin film emitter properties.

show abstract

Section: Resultsmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Characterization of sputter deposited thin film scandate cathodes for miniaturized thermionic converter applications

Zavadil¹,

Ruffner²,

King³

1999

AIP Conference Proceedings

View full text Add to dashboard Cite

show abstract

“…The emission coefficients range from 68 to 16 mA"cm-2"K-2and show a decrease by a factor of approximately 3 over the investigated temperature range. These values are a factor of 10-3to 104 lower than the theoretical value of 120 A.cm-2.K-zand considerably lower than a practical limit of 7 A.cm-2-K-2found for state-of-the-art metal coated dispenser cathodes [14]. This large discrepancy appears to be the result of underutilization of the available emitting surface area.…”

Section: Emission Properties Of Thin Film Emittersmentioning

confidence: 61%

Low work function thermionic emission materials

Zavadil¹,

King²,

Ruffner³

1999

View full text Add to dashboard Cite

NOTICE.This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government, nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, make any warranty, express or implied, or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represent that its use would not infringe privately owned rights. Reference herein to any speciilc commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government, any agency thereof, or any of their contractors or subcontractors. The views and opinions expressed herein do not necessarily state or reflect those of the United States Government, any agency thereof, or any of their contractors.Printed in the United States of America. This report has been reproduced directly from the best available copy. AbstractThermionic energy conversion in a microminiature format shows potential as a viable, high efficiency, "on-chip" power source. Microminiature thermionic converters (MTC) with inter-electrode spacings on the order of microns are currently being prototype and evaluated at Sandia. The remaining enabling technology is the development of low work function materials and processes that can be integrated into these converters. In this report, we demonstrate a method of incorporating thin film emitters into converters using rf sputtering. We find that the resultant films possess a minimum work function of 1.2 eV. Practical energy conversion is hindered by surface work function non-uniformity. We postulate the source of this heterogeneity to be a result of limited bulk and surface transport of barium. Several methods are proposed for maximu" ing transport, including increased fti porosity and the use of metal terminating layers. We demonstrate a novel method for incorporating fti porosity based on metal interlayer coalescence.

show abstract

“…В литературе имеется множество публикаций о свой-ствах так называемых скандатных катодов [4,5], содержа-щих с своем составе скандий в виде оксида или интер-металлида скандия, и которые при той же температуре, что и металлопористые катоды, обеспечивают получение на серийных катодах плотность тока до 100 А/сm 2 , а в " рекордных" случаях -до 400 А/сm 2 . Такие харак-теристики скандатных катодов открывают возможности создания принципиально новых типов электровакуум-ных СВЧ приборов, а также повышения параметров приборов существующих типов.…”

Section: Introductionunclassified

“…Несмотря на 50-летнюю историю создания и совершенствования скандатных катодов, в литературе отсутствуют экспериментально и теорети-чески обоснованные представления о физическом ме-ханизме работы скандатных катодов, необходимые для совершенствования составов и технологий скандатных катодов [5]. Настоящая работа и посвящена решению данной проблемы.…”

Section: Introductionunclassified

Физический Механизм Работы Скандатных Катодов СВЧ Приборов

Капустин¹,

Ли²,

Шуманов³

et al. 2017

Журнал Технической Физики

View full text Add to dashboard Cite

Методами электронной спектроскопии для химического анализа, спектроскопии характеристических потерь энергии электронов и оптической спектроскопии исследована электронная структура кристаллитов оксида бария, который определяет эмиссионные свойства как металлопористых, так и скандатных катодов. Установлено, что другие элементы (кальций, алюминий, скандий, вольфрам), входящие в состав катодных материалов, растворяются в оксиде бария, существенно влияя на его электронную структуру и соответ-ственно на эмиссионные свойства. Результаты исследований позволили сформулировать представления о физическом и физико-химическом механизмах влиянии скандия на снижение работы выхода скандатных катодов по сравнению с катодами других типов.

show abstract

Emission properties of top-layer scandate cathodes prepared by LAD

Cited by 136 publications

References 16 publications

Characterization of sputter deposited thin film scandate cathodes for miniaturized thermionic converter applications

Characterization of sputter deposited thin film scandate cathodes for miniaturized thermionic converter applications

Low work function thermionic emission materials

Физический Механизм Работы Скандатных Катодов СВЧ Приборов

Contact Info

Product

Resources

About