A RARE-EARTH-OXIDE MATRIX FOR EMITTING PERRHENATE ANIONS

A novel ceramic-like material has been produced and tested which has the property of emitting perrhenate anions for several thousand hours when heated in vacuum to temperatures between 1073 and 1173 K. Previously reported versions of this material were inferior to the material discussed here, probably owing to loss of perrhenate from reduction within the host matrix. The earlier materials, as well as the present materials, use barium perrhenate, a reasonably refractory compound, in a rare earth oxide matrix. The use of europium and ytterbium oxide as matrices for barium perrhenate improves the perrhenate anion emission properties of these materials by an order of magnitude when compared to the next best group of rare earth oxides. This improvement is credited to the fact that these rare earth oxides (in the +3 oxidation state) have stable +2 states to which they can be reduced, thereby serving as an oxidizing matrix to stabilize perrhenate. This indicates that europium and ytterbium +3 oxides can function as high temperature oxidizing matrices for chemical species which need to be maintained in an oxidized form.