High-intensity atomic oxygen radical anion emission mechanism from 12CaO · 7 Al₂O₃ crystal surface

12CaO·7Al₂O₃ (C12A7) crystal is an interesting material where a large amount of O^-(c) and O₂^-(c) can be formed and trapped in the cages when it is sintered in dry oxygen. The emissive features of this material including the emission species, temperature dependence, field dependence, emission branch ratio, emission stability, the effects of water on the emission intensity, have been investigated. The temperature and oxygen pressure dependences of the electrical conductivity have also been measured. The mechanisms of the O^- emission have been discussed based on the investigations of the emission and electrical conductivity features.