Transformation Toughening of Beta”-Alumina 830225

The fracture toughness and fracture strength of beta”-alumina are critical material properties for insuring reliable assembly, performance and lifetime of sodium-sulfur batteries in electric vehicle applications. The fracture toughness of the electrolyte is of major importance because it has been shown that the critical sodium ion current density for electrolyte degradation is proportional to the fracture toughness of the electrolyte to the fourth power. High fracture strength of the electrolyte is required for making and maintaining reliable seals to the insulating header. Greater fracture strength and toughness of beta”-alumina can be attained through transformation toughening while maintaining tolerable ionic resistivities.