An oxygen negative ion source of a new concept using solid oxide electrolytes

A novel oxygen negative ion source named solid oxide ion source (SIOS) is proposed. To demonstrate this concept, thermionic emission of oxygen negative ions, O-, from a bare surface of yttria-stabilised zirconia (YSZ) was studied with a mass spectrometer capable of detecting negative ions. The emission current was investigated at the temperature range 750 to 950 C under pressures of about 2 x 10 exp(-3) to 4 x 10 exp(-4) Pa. O- ions were emitted into a vacuum from the bare YSZ surface at elevated temperatures, the emission current increasing with temperature and applied voltage. From Richardson-Dushman plots, activation energy of the thermionic emission was estimated to be about 2 eV. In continuous operation, the emission current decreased with time, finally approaching zero; however, after intervals, the current recovered. On the basis of the results, a model for explaining the emission mechanism of O- ions is proposed. The model is based on three key processes occurring on the surface of the electrolytes: (1) formation of O-ions on the surface by electron capture of oxygen atoms provided by the migration of oxide ions across electrolytes, (2) accumulation of O- ions on the surface, and (3) emission of O- ions from the surface. 17 refs.