Galvanic Cells Containing Cathodes of Iron-Doped Beta-Alumina

Abstract

Galvanic cells of the form Na//~-alumina/Na20.11(Fe~A12-=O~) where x varied between 0.9 and 1.2 were operated at 120 ~ and currents of 50 mA/cm 2 could be drawn. The cells were electrochemically regenerative, and the cath-odes could be thermally regenerated. Initial open-circuit voltages varied be-tween 2.37 and 2.45V. Cells were discharged at constant current, and two distinct voltage regions were observed. The reduction process was investigated by MSssbauer spectroscopy. The lower voltage region was hown to involve the reduction of Fe 3+ to Fe 2+. The higher voltage r gion is possibly explained by the filling of holes in the valence band of the iron-doped spinel-type struc-ture, created during the sintering process. Sodium E-alumina Na20.11 A1203 has become in-creasingly attractive as an electrolyte in recent years due to its relatively high conductivity and its applica-bil ity to alkali metals (sodium in particular) as poten-