K. Daimon et al., Formation of La-2(SO4)(3)-Al-2(SO4)(3) solid solution and phase transitionof alumina formed by thermal decomposition, NIP KAG KAI, (9), 2000, pp. 657-659
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%.