engleski

Crystallization pathway of sol–gel derived zinc-doped mullite precursors

Zinc doped mullite precursors were sol–gel prepared in order to study the Zn influence on crystallization pathways of the spinels first formed at about 920–970◦C. Precursors were calcined at 700◦C andthermally treated at 1000–1300◦C and thereafter characterized (DTA/TG, PXRD, Rietveld refinement). Thermal treatment of precursors at 1000◦C initiates segregation of ZnAl2O4 from first formed Zn-rich gamma-alumina metastable solid solution. Remaining spinel reacts with amorphous silica yielding mullite ; thereby further enriching gamma-alumina on Zn. Thermal treatment affects Zn-doped gamma-alumina yielding crystallite size 11±3 and 28±4 nm at 1000 and 1300◦C, respectively. Parameter of inversion for ZnAl2O4, delta, increased from 0.05 to 0.20 upon heatingfrom 1000 to 1300◦C. SEM EDS analysis show the bodies sintered at 1600◦C reveal zinc deficiency due to Zn volatile nature. Electron microscopy (TEM, SEM) of sintered compacts exhibited microstructure with lower porosityhaving both elongated and equiaxial grains.

γ-alumina ; Zn-doped γ-alumina metastable solidsolution ; Gahnite ; Mullite ; crystallisation

nije evidentirano