INVESTIGATION ON TEMPERATURE DISTRIBUTION AND THERMAL STRESS OF BETA prime -ALUMINA UNDER CONDITIONS OF SODIUM ION TRANSPORT.

Temperature distribution and thermal stress in a sodium beta prime -alumina solid electrolyte under conditions of sodium ion transport are calculated using finite element method to clarify the Mode I degradation. A critical current density determined by the thermal stress is about 15A/cm**2 for the typical beta prime -alumina plate with 2 mm thickness in a sodium/sodium cell, even if no substantial crack exists at the surface of the beta prime -alumina. It is also shown that there is a formation of a high resistance layer at the surface of the beta prime -alumina, a partial formation of an electrically insulating film between the beta prime -alumina and sodium interface due to low wettability and/or the existence of the crack reduce the critical current density.