Rapid synthesis of inorganic [Ca24Al28O64]4+(e-)4 electride and its performance as an electron thermal emitter

We propose an effective and rapid route for synthesizing polycrystalline mayenite electride (C12A7:e(-)) in dense bulk. C12A7:e(-) bulks with high-density electron doping were obtained via a comprehensive method, which combined Ti powder treatment with spark plasma sintering (SPS) process under a 10(-2)Pa vacuum. The resulting electride, which exhibits an electron concentration of similar to 2.3 x 10(21)cm(-3), an electrical conductivity of similar to 1.38 x 10(3)S/cm at 300 K, and an absorption peak at 2.5eV, was obtained via SPS process at 1150 degrees C for 20 min. Furthermore, thermionic emission from a flat surface of C12A7 electride was examined at temperatures of 973-1373 K and acceleration electrical field of 3000-35000 V/cm in a 10(-5) vacuum. A large current density of 1.68 A/cm(2) was obtained in the thermionic emission with an work function (phi(wp)) of 2.13eV for an applied electric field of 35000 V/cm. Moreover, the emission with a current density of 1.68 A/cm(2) was stably sustained for 30 h. These results not only suggest an efficient method for fabricating high-quality mayenite electrides but also pave a way for various applications including thermionic emission.