Thermionic Electron Emission from a Mayenite Electride-Metallic Titanium Composite Cathode

A composite thermionic cathode consisting of 12CaO center dot 7Al(2)O(3) (C12A7) electride and metallic Ti (70 : 30 vol %) was fabricated as an electron emitter, and the thermionic electron emission properties were evaluated. A high emission current density of similar to 1.4 mA cm(-2) was achieved at 700 degrees C with an electric field of 4.0 x 10(4) V cm(-1). The work function evaluated from the Richardson-Dushman equation was 2.1 +/- 0.3 eV, which coincides with the value for pure C12A7 electride and is lower than that for LaB6. Unlike the pure material, the composite has ohmic contact with metallic materials, and can be heated directly by electrical current. (C) 2013 The Japan Society of Applied Physics