Results from the microminiature thermionic converter demonstration testing program

King, Donald B.; Luke, James R.; Wyant, F.J.

doi:10.2514/6.2000-2844

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…Examples include miniature thermionic diodes (King, 2000) used as small-scale power sources and high frequency microwave generators (klystrons) for particle acceleration or directed energy applications. The electron source community has optimized macroscopic cathodes based on impregnating a porous tungsten matrix with barium oxide for display applications (Thomas, 1990).…”

Section: Introductionmentioning

confidence: 99%

A novel thin film dispenser cathode for thermionic emission

Zavadil¹,

King²,

Ruffner³

2001

AIP Conference Proceedings

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Abstract. A thin film dispenseror micro-dispensercathode can be generatedusing standard rf sputteringdeposition technology. These films are compositionallymodulated structures based on W and a multi-componentBa oxide. Annealing to temperatures horn 900 to 1300K results in Ba reduction, transport and diffision across the emitter surface.A finite temperaturerange exists(< 1200K)where a uniformRe coatingcan be retainedat the emittersurface. The metallic coating results in a nearly homogeneouswork finction based on emission characteristics.These films produce stable emissionat higher temperatures(2 1200K)where the uniform Re coating is lost. Analysisof emission properties yield a work function of 2.2 eV and an apparent emission coefilcient of 6 A"cm-2"K-2 after annealingto 1200K.This high apparent emission coefficient yields a film suitable for milliwatt power generation applications. MicrominiatureThermionicConverters(MTCS)are one potentialapplicationfor these films.

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Section: Introductionmentioning

confidence: 99%

A novel thin film dispenser cathode for thermionic emission

Zavadil¹,

King²,

Ruffner³

2001

AIP Conference Proceedings

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“…High efficiency at low temperature requires the use of a low work function, highly electron emissive cathodes in small gap diodes where space charge fields cannot develop. Using such a cathode, calculations show that the efficiency of a microminiature thermionic converter (MTC) with an interelectrode gap of one to ten microns can exceed 20% [1]. MTC'S require a thin fdm emitter that can be integrated into the fabrication of the diode at a given thickness to yield a high tolerance gap distance.…”

Section: Introductionmentioning

confidence: 99%

Low work function thermionic emission materials

Zavadil¹,

King²,

Ruffner³

1999

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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.

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Results from the microminiature thermionic converter demonstration testing program

Cited by 2 publications

References 2 publications

A novel thin film dispenser cathode for thermionic emission

A novel thin film dispenser cathode for thermionic emission

Low work function thermionic emission materials

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