Phase formation of Na+-beta-aluminas synthesized by double zeta process

Na+-beta-aluminas in the Na2O–Al2O3–Li2O ternary system were synthesized by double zeta process and the dependence of the crystal phase formation on the composition and the calcination temperature was studied. For the synthesis of Na+-β/β″-alumina, sodium aluminate varying compositions of [Na2O]:[Al2O3]=1:4–1:6 and lithium aluminate in the forms of Li2O·5Al2O3 with different amounts of Li2O (0.35–0.45wt%) were well-mixed and calcined at temperatures ranging between 1300 and 1600°C for 2h. The β″-alumina fraction appeared to be approximately 10% higher compared to the conventional solid state reaction, showing around 70% of β″-alumina fraction. These values increased about 10–15% by additional heating near the binary eutectic temperature for a short time.