The chemical stability of beta/beta″-alumina in sulphur/sodium polysulphide melts

Experiments in which β″-alumina ceramic is exposed to sulphur or sodium polysulphide can indicate the formation of a reaction layer. Analysis of thermodynamic data and kinetic studies indicates that the reaction layer is not a corrosion but a surface reaction caused either by traces of second-phase sodium aluminate in the ceramic or by equilibration of Na2O activity between the ceramic surface and the sulphur melt. The absence of corrosion is supported by the evidence of long-term testing of β″-alumina ceramics as electrolytes in Na/S cells.