Thermionic converter and methods of making and using same

A thermionic converter, comprising:

• a collector;
• an emitter;
• a gap disposed between the collector and the emitter;
• an electrical connection means connecting the collector and the emitter;
• and,
• cesium disposed in the gap adjacent the emitter,
• wherein:
• the emitter comprises a cold worked metal substrate capable of emitting electrons when heated to temperatures of 800° C. or greater,
• the cold worked metal substrate is cold rolled in the direction of grains of a target crystallographic orientation having the lowest surface energy and highest bare work function;
• the grains of the target crystallographic orientation are thermally grown such that the grains of the target crystallographic orientation represent at least 40% of the surface area of the metal substrate;
• and
• the grains of the target crystallographic orientation are etched to form a patterned surface, thereby increasing the surface area on a face of the grains.