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Ceramic electrolytes derived from /?-alumina are cracked by electrolysis under certain conditions. Cracks form only when Na+ ions migrate through the ceramic and are converted to metallic Na, as in the charging of an Na-S battery. The origins of mechanical damage are postulated and examined. A plausible mechanism consists of ceramic dissolution at preexisting surface cracks; it depends on the interaction of capillarity, stress, and selective removal of electrolyte from crack tips by effluxing Na. Relative solute fluxes are calculated for each contributing process. The proposed model is shown to account for many of the experimental observations, most notably a threshold current density below which no degradation is apparent.

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