Surface Electrical Conductivity of Single Crystal Spinel in Cesium Vapour.

The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapour, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs <1>. In this report we describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapour at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.