Calciothermic synthesis of inorganic [Ca24Al28O64]4+(4e−) electride from solid-derived precursor

Abstract

[Ca24Al28O64]4+(4e−) has great application prospects in electron emission and catalyst support, but suffers prolonged synthesis time and complicated multistep process. In this work, a direct and efficient calciothermic reaction was utilized for the rapid fabrication of subnanoporous electride ~ [Ca24Al28O64]4+(4e−) directly from a novel mixture of CaAl2O4 (CA), CaO, and Ca powders under milder conditions (e.g., sintered at 1070 °C for 10 min in a vacuum). Phase-pure CA derived from calcinating was for the first time used as a precursor for the synthesis of dense C12A7:e− ceramic. The as-prepared C12A7:e− exhibited an electron density of ~2.3 × 1021 cm−3, covering the metal-insulator transition. The electron injection in the as-sintered C12A7:e− was verified by electron paramagnetic resonance analyses. Moreover, thermionic emission began to occur at 700 K and increased to 1.8 A/cm2 at 1373 K when an extraction electrical field of 3.5 × 104 V/cm was applied. This demonstration shines new light on studies of formation avenues of polycrystalline C12A7:e− structure.