DEVELOPMENT OF HIGH-CURRENT ION EMITTER USABLE IN AIR

为研制可用于空气的离子源，研究了固体电解质的热离子发射机理。研究结果表明：A沸石中碱性阳离子的热发射导致沸石中过量阴离子的积累，表明热离子发射是一种非化学计量反应。由于Cs的电离能很低，Cs离子交换丝光沸石在1300K时表现出很高的热离子发射效率。然而，在&gt；1000K下丝光沸石表现出很低的效率和低的离子电导率。这是由于以下原因：离子从固体表面发射，会使离子空位带相反的电荷。发射离子和相反电荷之间的库仑引力由于导电离子围绕相反电荷的迁移而减小，因此固体电解质通常表现出较高的热离子发射效率。然而，如果传导离子的迁移太慢而不能跟随发射过程，这一过程就不起作用。因此，Cs^离子在低温下几乎不发射。

The mechanism of thermionic emission from solid electrolytes has been studied for developing ion sources possible to be used in air. The following results has been obtained from the study.The thermal emission of alkaline cations from zeolite A causes the accumulation of excess anions in the zeolite, which indicates that the thermionic emission is a nonstoichiometrical reaction.Since the ionization energy of Cs is very low, Cs^+-exchanged mordenite shows very high efficiency of the thermionic emission of Cs^+ at > 1300 K.However, the mordenite at > 1000 K shows very low efficiency together with the low ionic conductivity. This is due to the following reason : Emission of an ion from a solid surface leaves an ion vacancy with the opposite charge. The Coulombic attractive force between the emitting ion and the opposite charge is reduced by the migration of conducting ions around the opposite charge, so that solid electrolytes generally shows high efficiency of thermionic emission. However this process is not operative if the migration of conduction ions is too slow to follow the emission process. The Cs^+ ion is therefore scarcely emitted at low temperature.