Solid solution of Zr into anhydrous Al-2(SO4)(3) crystal lattice and eta ->alpha phase transformation of Al2O3 formed by thermal decomposition of thesulfate solid solution
K. Daimon et al., Solid solution of Zr into anhydrous Al-2(SO4)(3) crystal lattice and eta ->alpha phase transformation of Al2O3 formed by thermal decomposition of thesulfate solid solution, J CERAM S J, 107(1), 1999, pp. 41-46
More than 60 mol% Zr4+ ion (ZrO2/ (Al2O3 + ZrO2)) is soluble into anhydrous
Al-2(SO4)(3) crystal lattice. The apparent crystallite size decreases with
increasing Zr4+ content, and the thermal decomposition temperature reduces
at contents of zirconia > 20 mol % , Alumina/zirconia composite powders, i
n which an amorphous zirconia phase is dispersed in a matrix of fine eta-al
umina particles, are obtained by thermal decomposition of the sulfate solid
solution. Tetragonal phase of zirconia crystallizes at 1100 degrees C and
the crystallinity increases with increasing the temperature of the heat-tre
atment. When mono-dispersed ultra fine particles of zirconia are added to e
ta-alumina formed by thermal decomposition of pure anhydrous aluminum sulfa
te, the eta-->alpha phase transformation of alumina is suppressed, and the
effect increases with increasing the amount of the additive. On the contrar
y, a small quantity of ZrO2 < 1 mol % drastically suppresses the phase tran
sformation of alumina formed by decomposition of sulfate solid solution. Bu
t, when ZrO2 content is more than 1 mol %, the eta-->alpha phase transforma
tion of alumina is accelerated, The acceleration effect becomes larger with
increasing the content of ZrO2.