High Density Hydroxyl Anions in a Microporous Crystal:  [Ca24Al28O64]4+·4(OH-)

Abstract

By retreating the C12A7-O- microporous crystal ([Ca24Al28O64] 4+·4O-) in a high-temperature (1350 °C) and water vapor environment, almost 100% O- and O2- anions in C12A7-O- have been substituted by the OH- anions, leading to the formation of a high-intensity OH- emission material, [Ca24Al28O64]4+·4OH- (C12A7-OH-). The formation of OH- in C12A7-OH- was identified by investigating the anionic species both on the surface and in the bulk as well as its emission features with Fourier-transform IR absorption, electron paramagnetic resonance, and time-of-flight mass spectra. The concentration of OH- anions in C12A7-OH- is estimated to be more than 7 × 1020 cm-3. Furthermore, a sustainable and stable OH- emission current of 11.7 μA/cm2 from C12A7-OH- has been obtained at a sample surface temperature of 780 °C under an extraction field of 1300 V/cm. The emission features of C12A7-OH-, such as temperature and field effects, have been also investigated. It is expected that the present material could be practically u...