Improved Microminiature Thermionic Converter Using Low Work Function AlGaN Electrodes

"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 generationis 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 intovacuum. 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 thelow 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 largerpower 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. Thethermionic 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