Improved Microminiature Thermionic Converter Using Low Work Function AlGaN Electrodes

Period of Performance: 03/21/2003 - 09/21/2003


Phase 1 SBIR

Recipient Firm

Astralux, Inc.
2500 CENTRAL AVE., # 286
Boulder, CO 80301
Principal Investigator


There is a general need to generate high energy density electrical power sources for space, aircraft, ground and naval vehicles, as well as to convert the heat already present in high temperature sources into electrical power. Thermionic power generation is a very attractive solution to both needs. Thermionic emission typically occurs from metal surfaces when the temperature of the metal excites the electrons to energies exceeding the metals' work function, allowing the electrons to be emitted into vacuum. The work function of most metals fall in the range of 4-5 eV, requiring temperatures exceeding 2000K to produce significant thermionic emission. Astralux proposes to build and test a revolutionary new cathode material based on AlGaN. Due to the low work function of the AlGaN, much larger emission currents can be achieved at a given temperature than would be possible with a simple metal emitter. When compared to MTCs fabricated from metal/metal oxide electrodes, our MTC will demonstrate larger power conversion by increasing the average voltage of emitted electrons, increasing the emitted current and reducing the space charge effects. These improvements will lead to a device capable of thermionic emission at temperatures well below 1000 K. The thermionic power generator addresses growing markets where the needs of remote, off-grid power continues to increase together with the overall need for power. Thermionic power may be able to supplement, or replace, photovoltaics in space and terrestrial power applications as well as provide additional power to utilities to meet incremental growth needs. The photovoltaics market is over $1 billion annually.