Results from the microminiature thermionic converter demonstration testing program

Research is in progress to develop microminiature thermionic converters (MTCs) using semiconductor integrated circuit (IC) fabrication methods. The use of IC techniques allows the fabrication of MTCs with an emitter to collector spacing of several microns or less and with emitter and collector materials that will have work functions ranging from 1 eV to 2 eV. Theory predicts that the small emitter to collector spacing and highly emissive low work function electrodes should allow the conversion of heat energy to relatively large electrical current densities (up to tens of Amps/cm²) at relatively high conversion efficiencies (15-25%). Tests of prototype MTCs have demonstrated energy conversion at several emitter temperatures. The power generated is less than expected because of less than optimal emission characteristics encountered with the low work function materials used for the first MTC prototypes. Efforts to improve electrode emission characteristics are in progress