Production and characterization of polycrystalline (Na, Ca)β′′ -alumina

Abstract Polycrystalline (Na, Ca)β″ -aluminas with different calcium contents were produced from commercial Naβ′′ -alumina (Ceramatec Inc.) by ion exchange in suitable mixtures of NaNO 3 and Ca(NO 3 ) 2 . The extent of crack and pore formation could be reduced by increasing the calcium content gradually from one equilibrium concentration in the solid electrolyte to the next - higher one. The equilibrium distribution curve was determined for the polycrystalline materials and compared with measurements on single crytals. Thermogravimetric measurements were made on fully-exchanged samples. The curves of the specific conductivity versus the extent of exchange suggest that the Na + ion is the conducting species in a wide range of soda content. The transition to the predominant conduction by the Ca 2+ ion occurs in a relatively narrow region at high extents of exchange.