Intense thermal field electron emission from room-temperature stable electride

Thermal field emission (TFE) from a flat surface of 12CaO∙7Al2O3 (C12A7) electride was examined at temperatures up to 900°C and applied external voltages of 0–6kV in a 10−5Pa vacuum. TFE started to occur at ∼650°C and steeply increased at ∼900°C to reach ∼80μA (∼1.5Acm−2) when an extraction field of 105Vcm−1 (an extraction voltage of 6kV) was applied. The work function estimated from the Richardson–Dushman equation was ∼2.1eV, which is rather smaller than that of LaB6 (∼2.7eV). It is experimentally confirmed that the emission with a current of ∼50μA (from a 80μm diameter area) was stably sustained for more than 90h. The efficient and stable emission at relatively low temperature in a moderate vacuum atmosphere strongly suggests that the C12A7 electride has high potential for TFE applications.