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 10−2Pa vacuum. The resulting electride, which exhibits an electron concentration of ∼2.3 × 1021cm−3, an electrical conductivity of ∼1.38 × 103 S/cm at 300 K, and an absorption peak at 2.5eV, was obtained via SPS process at 1150 °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/cm2 was obtained in the thermionic emission with an work function (φWF) of 2.13eV for an applied electric field of 35000 V/cm. Moreover, the emission with a current density of 1.68 A/cm2 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.