Formation of La-2(SO4)(3)-Al-2(SO4)(3) solid solution and phase transitionof alumina formed by thermal decomposition

Solid solutions of La-2(SO4)(3) and Al-2(SO4)(3) were prepared by rapidly d rying mixed aqueous solutions using micro-wave heating. The La3+ ion is sol uble into the anhydrous aluminum sulfate crystal lattice up to about 6 mol% . On heating the thermal decomposition starts at 830 degrees C for the pure Al-2(SO4)(3), while at 760 degrees C for 6 mol% La-2(SO4)(3) contained Al- 2(SO4)(3). The anhydrous aluminum sulfate solid solution thermally decompos es into the eta-Al2O3 without any other crystalline phases. The LaAl11O18 i s formed after heating the desulfurized product at 1300 degrees C without f orming LaAlO3 when the content of La2O3 is less than 6 mol%. The La3+ dopin g increases the stability of eta-Al2O3 at high temperatures. The phase tran sformation of alumina takes place above 1350 degrees C when the amount of L a2O3 is 5 mol%.